It really isn't that complicated. But there are certain criteria that have to be met. These are living, breathing creatures that are babies. And essentially orphans at that! You are their mother.
Chicks have to be kept warm and dry at all times. Cold, wet equals DEAD. Garage with heat lamp, guest bath in the tub with heat lamp. I've used tub with a 6 sheet layer of newspapers, heating pad set on medium to low, covered with another 6 sheet layer of newspapers. Chicks will hang around on the heat pad if they need to. After a few weeks, they will be ready for no heat pad. While they are inside, you can start building the coop or chicken tractor. Ready to buy coops or tractors may not fit your needs or budget. Should have roosting bars, structure covered at least over the roosting bars to protect against the elements. Cold, wet equals dead. Once the night temps are in the 60's AND the girls are fully feathered, they will be ready for the coop or chicken tractor.
Now, the ones from the retail outlets have survived shipping and a few days at the store. Let the store absorb the loss of those who were not strong. Look for lively chicks, pecking at food or drinking. Avoid the ones who peep loudly by themselves. They are broadcasting that they have a problem.
You say you want 4. You should get at least 6 (and some retailers will only sell minimum of 6). The reason for the minimum is so that they can help kep each other warm. 10 would be best in my opinion. Chickens are also social animals. Ten girls will allow for a couple of losses - not planned, but it does happen.
The time they spend inside can be used to your advantage. You can train them with food. They will recognize your voice if you talk to them when you feed them. Just use normal tones. After a week, they will recognize your voice.
Good luck,