This is a bit complex question. Shortly I can answer this way:
Each node needs at least connectivity tools. You are not saying what SQL Server version you use. In general however there is always required minimum. So you should use the setup and load minimum. Next depends on your requirements you need to make sure that there is at least <b>NT Network Authority\Network Service</b> Log in setting. That you can set through <b>SQL Server Configuration Manager</b>. Next you have to decide what the <b>Server Authentication</b> you prefer – <b>Windows Authentication Mode</b> or <b>Windows and Server</b> mode. That you can change from server properties. If you selected Windows and Server mode then you can create the logins in the server and use them to connect however there is Windows Only Authentication preferred. If you are not going outside of you network you can actually choose Windows and Server mode if is more convenient for you. When all is set and you want to connect to the server from NET application then you need to use <b>Microsoft SQL Server (OLE DB)</b> Provider for <b>SQL Server 2000</b> and <b>SQL Server Provider</b> or <b>Native Provider</b> for any hirer version of the Server.
That is shortly all. If you need more info regarding each subject I mentioned her I believe that the best it could be to read about it in <b>Books Online</b> related to the version of SQL Server. Like I said above this is complex subject and is difficult to answer in several words.