Bad Pun Dog

In your profile, under the "settings" tab, it should display your current username. If you're eligible to change it, you should just be able to click in the field and type what you want. Also, you can only change it once, so if you did when you made your account, you probably won't be able to.
Idk for sure though, it's been a while since I did it...

I didn't see my username in the google plus settings so I can't change it. But thank you anyways. :)

This is good