How to set up a simple network?

Please, can anyone help me to set up a network?
I have 3 computers that I'd like to network.

1. Desktop 1 (connected to a wireless gateway with a network cable)
2. Desktop 2 (connected wirelessly)
3. Laptop ( connected wirelessly)
3. Desktop 2 and Laptop are also connected to each other with 5e patch
cable.

I'd like my Desktop 2 to be able to communicate with Laptop ( move files
back and forth). I'd also like my Laptop to have access to my multiple
external hard drives connected to Desktop 2.

All I have right now is "Limited or no connectivity"

Please help or direct to a source that can help.

Thanks a lot in advance!