Ok, here is my best try. Wish I could just show you! Left and right is on the person putting it on. . .
Take off both fronts from the back straps. Put both backs on, one on top of the other. Make them as big as you can. Pull one set of straps all the way to the left. Pull the other two all the way to the right.
Reach your hand through the front corner of the straps of the left set, down where the white plastic thing is attached, from right to left, and pull the right white plastic tab thingy through, so the straps are cris crossed in the front of you.
Take a deep breath and tell the girls you will soon be ready for them.
Attach the front to the left side. attach the far left front to its own set of straps. Attach the thingy into the rings and the snap on the far left. Left side is now half attached. Put in girl A and finish attaching her bjorn to its own straps, but don't snap the right snap. Tug her to the left.
Attach the front of the right bjorn to its back with the white thingys. Put her left T bar through her loop, but you'll do it over top of the first set of straps.
Have I lost you yet? I'm doing this as I type, and it is really hard to describe, but I'm hoping you get the picture. . .Add girl B to the picture, and finish hooking and snapping everyone in. At this point, I usually have two or three people stopping to watch me in the grocery store parking lot and my son screaming to get out of the car too, but I have to dance and jiggle a bit to get them settled.
Good luck. I see you are a new member. How old are your girls? Mine are four months now. I have shopped a lot with them like this facing me. I'm not sure how it will work facing outward, but I like shopping with faces in, since people want to touch them too much for my liking. This is not easy on the back, but sometimes it is all that will keep them happy while I shop or chase my son around the park. I think you have another one too, but don't remember how old. This way I can put my son in the front of the shopping cart. Isn't life fun?
Don't bend down to pick something up!!! Let someone else unload your groceries in the car!!!