At this time we don't offer an option to change usernames.
If you want to upload videos under a different name you will have to create a new account.
---
Alternatively, you can create a channel within your existing account HERE:
The Name you choose for your channel will determine your URL. If you name your channel "MyRumbleChannel" your channel's link will be "Rumble.com/MyRumbleChannel"
The Title is what other users will see in your banner; you can choose "My AWESOME RUMBLE Channel" if you want.