You can take them orally, vaginally or both. I have one MW who strongly recommends orally, another who thinks vaginal is the only way it's effective and a third who recommends both just to be safe.
I'm currently taking 3 a day orally and just DTD a lot instead of using the capsules vaginally. When I was inserting them, I'd just poke a hole with a pin and insert. I do use the oil as lube when we DTD so it's sort of a two for one.
It's not going to hurt anything or put you into labor but it should help your cervix thin and prepare. I'm pretty sure you can just keep up-ing the dose as you get further along and since you're so far along already, I might start with more than one orally. I'm pretty sure you can't OD on it.