Because Mac OS X Samba built in, it is fairly easy to connect to Windows networks and join workgroups. To begin the set up, open the Directory Access utility under Applications -> Utilities. (If the window is locked which is indicated by a closed padlock image in the lower left-hand corner of the panel, click on the padlock to unlock it.)

Select SMB/CIFS and click "Configure...". Type in the name of the Windows workgroup that you want to join in the Workgroup field, enter a WINS Server (if appropriate) and click OK, then Apply and you should be joined into that Windows workgroup on your Mac.