I found there's no need to bother with homegroups.
Just set folders or whole drives to be shared. After a while, sometimes several minutes, you should see the other computers in network 'folder'.
If they don't appear try inputting the computer name in the address bar, with 2 backwards slashes e.g. \\maincomputer

Set up the printer directly attached to each machine first, then when it's on any other computer (and set to share there) you should be able to print to it.