What version of Access are you using (2007 or 2010)? Also what sort of network are you connected to? The easiest way to connect to a database is by using Integrated Security, but that generally means you need to have an NT domain running where the network logins are administered from a domain controller server. Also, you probably need to define each user with SQL Server security and establish the appropriate permissions for each user. That should be done using SQL Server Management Studio unless you are very familiar with the system sprocs. That is the likely explanation for only being able to read tables, and not seeing the drop-down lists. If you are using a single login, then you can't tell who does what to what.

The usual approach is to create an ODBC data source on each workstation that uses the database. That is done using the utility under Administrative Tools in Control panel, and chosing the database and server you are connecting to. The tool under External Data that you are attempting to use is an upsizing tool that takes an Access table and upsizes it to SQL Server. If you are using Windows7 workstations, you want to do it as a User DSN, not a System DSN, and the SQL Server driver in Windows7 is actually a bit newer than the Native 10 client. If workstations are on XP or Vista, then you do want the Native 10 client installed.