Can't change the logon into SQL SSMS

I've never considered opening SQL SSMS with any other account, but now that I'm trying to do that, I can't figure out how to do it. This is the panel I'm speaking of:

What must I do to be able to open SSMS with a different domain account? The User name box is greyed out and can't be changed.

Solution

Find where you have management studio installed on your machine (ssms.exe)

Hold down the shift key and right click it. In the pull down menu you will see the option to run it as a different user.

The shift-right click combo to run as a different user is available for executables and there are registry modification available for Windows 10 users launching apps that do not run for a legacy ".exe"