First, get all systems to connect to your WiFi router.
This will put them all on the same 'subnet', aka the router's network. If the router address is 192.168.1.1, then every connected system will have an address starting in 192.168.1.X
Second, decide which system will be the primary sharing device - - the one holding the largest amount of shared files.
This one will be the one that every (or almost every) one will access for the shared data. You should arrange to have a fixed address for this system (more on that later).
Next, pick the folder(s) which contain files to be shared (and that can be on more than just one system), and marked it as Shared
(for r/o or full control).
Once a system is on the routers subnet AND shared folders have been setup, Users can Map Shared Drives as they need.
btw: a shared printer is slightly different but handle that when needed.