I agree with the PP that you can learn how to cook if you can read and measure. I suggest starting with a basic cookbook which gives you the "vocabulary" of techniques. (Sorry I can't recommend one!) For instance, how to measure flour, saute onions, etc. Make sure that you have a set of measuring cups, and a set of measuring spoons. Remember this rule: cooking is an art, baking is a science. Often you can substitute ingredients, change things, or be less precise with cooking. But with baking it is always best to follow the recipe exactly.
I actually know how to cook pretty well, but actually planning all our meals has been a recently acquired skill!! I have learned that planning ahead is the key.
Okay, sit down with your basic cookbook, a notebook or stack of paper, and a pen or pencil. You are going to make a list of possible menu items that you know how to cook, a grocery list, a menu plan for the week, and a list of things you would like to learn how to cook.
First of all, start your grocery list with items that you know you need. For instance, if you eat Cheerios for breakfast every day, put them on the list. If you drink milk, put that on the list. If you buy bread, ditto. These are your staple items that you buy every week. I usually have staple items for breakfast and lunch--for example, cereal and milk or eggs and toast for breakfast, a sandwich and fruit or dinner leftovers for lunch.
Now make a list of things that you usually eat and know how to cook on a separate piece of paper. Focus on entrees. Even if they are simple, like spaghetti with sauce from a jar, put them on the list.
Leaf through your cookbook or on the internet, and start making a list of simple recipes that you would like to try. Stick with entrees for now, and don't go for anything with exotic ingredients. Perhaps just look for a new way to season something you already can make. (Maybe a different way to make chicken--something like that.)
Take another piece of paper and write each day of the week down, with room underneath it to write your dinner menu items. Look at the list of things you can cook, and pick an entree for each day's dinner and write them down. I usually decide on the main dishes for dinner for the entire week, then go back later and add side dishes or vegetables afterwards, so I don't get bogged down. Once you have the main entrees, you can then go back and figure out what to serve with each main dish. For example, if Monday you are going to have spaghetti, you might also want to serve a green salad and some French bread or garlic bread. If you are going to make baked chicken, you might also want to make mashed potatoes and some green beans. To expand your cooking repertoire, on the day of the week that you have the most time (say on Saturday your DH is home and can watch the kids for you) plan to try a new dish from the list of new dishes. ONLY TRY ONE NEW THING AT A TIME!!! This is one of the cardinal rules of cooking! It is also up to you how much you vary your weekly menu--I tend to try not to repeat meals more than once a month or so unless it's something that we absolutely LOVE, but some people keep the same menu plan every week. I think if I had little kids that might be helpful.
Anyway, once you have the menu planned, it's time to finish the grocery list. Look at your recipes for each day and check to see what ingredients you already have in the house. If you do not have them, you will put that ingredient on the list.
One thing I have started doing to save money is planning meals around what is on sale. For example, my grocery store puts it's weekly sales flyer out on Wednesdays. These are called "loss leaders" because they are items that the store often marks down to the point that they lose money on them--the idea is that you go in for the sirloin at 30 cents a pound and end up buying all the other, regular priced groceries while you are there! Anyway, I either get the sales flyers in the mail (or actually I can check it online!) and see what is on sale that week. This helps give me ideas. For example, if there is a great sale on broccoli, I might make broccoli instead of another vegetable. If turkey breasts are on sale, I might decide to buy one and make that one night. Also, I have discovered that the freezer is a wonderful thing! If you are going to make something that will freeze well, like chilli or soup, really consider making a double batch and freezing half of it for another night's dinner. It doesn't take much more effort, and gives you twice the meals.
Anyway, one thing I have found helpful is a site called frugalmom.net. I also get my menu planning sheets from there--she has some that are just like blank calandar pages that you can print, just write in the date and the meals for that month. I use the monthly one, but I only put in meals a week at a time. Also, save your menu plans once you are done with them, you can use them in following months to give you ideas when you are drawing a blank!