Audit user activity in SQL Server
If i understand correctly, you want to see all activity from a single user.

The quickest would be a profiler trace filtered to that user, start a trace and in the Event Selection and Column Filters add the user under "Like" in the LoginName filter, or NTUserName if appropriate.



Beware of overhead when using profiler in production it can be resource hungry.

If you want something more long term, you can look into auditing. Here is a useful tutorial for Select Statements but there is much more you can do with it.

Auditing Select Statements 2008