After a server has been set up how do you connect clients to that server over a LAN? Do you have to install extra software? Is a LAN the best way to connect the systems or should I use some other method of connecting computers to the server?
First you must be an administrator on the domain to which you wish to connect the pc. You must also have your user name and password.
Go to the client pc, click on start, then right click on my computer and click on properties. This generates the System Properties window. Go to the Computer Name tab in System Properties. Near the bottom of this window is the choice "to rename this computer or join a domain click here". Click there and follow the directions. You must enter the domain name when prompted, enter an administrator user name and password and you should be successful.
The above assumes you have a Windows pc. It cannot be XP Home. There is no other software needed. I have not connected MAC pcs to the server and I believe, but do not know for sure, that you must have some software loaded for these to work.
The clients must be on your LAN first. If they are not in the same location and on the same LAN you have a lot of other work to do but that is beyond the scope here.
Once the computer is on the LAN, make sure you have the user name and password of the intended user loaded in Active Directory.