As long as all of your PCs are on the same subnet (ex. 192.168.1.x), all you have to do is right-click on a folder you want to share, give the share a name, then access the share from your other PCs using \\hostPCname\shareName from the 'Run' box to open an Explorer window to there.
Additional steps may include adding individual users or the Guest account to the folder shares' permissions if you use different logins from different PCs or have multiple people you want to give access or different permissions to.