Plese, how can I change my logged user on PC?

Everytime I launch the pc version it shows a username that I created for test purpose, now I want to log in with my xbox one microsoft account as it does have S1 and S2 ultra versions, but have been trying since yesterday to no aval.

Please help me out.

You need to log out of that profile in the Xbox app, and sign in with the correct profile. No way to do it in Killer Instinct itself.