Thanks for the pictures, those help a lot. That's going to be a great coop! But, you won't need an outdoor space for your chickens until they're about 6 weeks old. Based on what you've said so far it sounds like you're looking for some specific next steps. That's what I'm going to try to give you. I can't give you an exact step-by-step, but I can get you going in the right direction.
Job #1 right now is to get a brooder set up for your babies to live in when they get to your house this weekend. By what you've shared I'm going to say that a plastic tub brooder is probably going to be the easiest solution. Do a search on Google Images or Pinterest for 'plastic tub brooder' to see what one looks like (but don't look too long, cause those results get off topic and confusing pretty quickly). Then make a list and head off to your local home/farm store to do some shopping. Below is a short list to get you started.
- large plastic tub (storage solutions dept)
- hardware cloth ~0.5 x 0.5 (or wire mesh, same thing)
- pine shavings, either fine or regular is fine, not ceder (pet dept)
- heat source (more on this in a second)
- quart size chick feeder
- quart size chick waterer
- chick feed (ask your store what kind)
- raw apple cider vinegar (Bragg's or similar with the "mother" on the label)
For the tub, get the biggest one you can move.
For the heat source your choices are either a heat lamp, heat plate, or heat pad. If you've got little ones and/or you're going to be setting your brooder up inside I'd avoid the lamp.
The ratio for the apple cider vinegar I think is about a tbsp per gallon water.
That'll get you through the first two to three weeks. They grow fast so that tub won't hold 10 chicks much longer than that. So, over the next few weekends maybe you can get your brother to come over and help you wall off part of your shed to make it a coop. We can talk more about that later. Brooder is job #1.
Now, go get started and post some more pictures. You can do this!
Supplemental reading if you don't think it'll add to the overwhelm. If you're at all concerned about that, do. not. click. Just make your list and go shopping.