I just don't know how to change my username on Minecraft pocket edition.
If you have the account linked to your Xbox account, you can go to the Xbox website to change your GamerTag which will in turn change your Minecraft PE Username as well
When on the title screen;
- Click settings
- Click profile
- Change your name
- If you are connected to xbkx live, you will have to disconnect first or change your gamer tag which costs money.
From the main menu, tap Settings, then press Profile (under the General category). At the top of the of the page will be a name box. Tap it to edit your username.