By following the last step, you connected to the SQL Server machine called IISQLSRV, using your account.
You type your query in the window in the upper right labeled Query. Type Ctrl-E to run the query (or click on the little green arrow on the menu). If everything worked alright, you should get back the results of the query - some tuples.
In Windows, goto Start, Programs, Microsoft SQL Server, Enterprise Manager.
On the Console Root, expand Microsoft SQL Servers, then expand SQL Server
Group, then expand IISQLSRV (Windows NT), and finally expand the Security Folder.
Click on Logins.
Find yourself (your UW CSE login) and right-click on your username. From this menu, select properties. You can type in your new password in the password field, just overwrite the old one. Once you click OK, you will be prompted to re-enter the password. Do so, click OK and you should be all done. If you're nervous, log out and re-log in with your new password.