You can run your test once you've set up your test configuration and created your users.
-or-
You must wait for each client on the computer to finish processing.
You can also run the Load Simulator in unattended mode by typing the following at the command prompt.
LoadSim simfile testname /q
where simfile is the name of a .sim file that will be used and testname is the name of a test specified in the .sim file. If this is not specified, the .sim file is opened but the test is not run.