Hi @Player588082860 & welcome to the forums! 
Changing ones forum name is covered in our topic: [HOW-TO] Change Forum Name in Official Microsoft Flight Simulator > Forum Navigation :
FYI, your forum name is tied to your Xbox Gamer Tag, once you change your Gamer Tag log out and back into our forums and the change should take effect.
Please visit the Xbox Support Website for information on changing your gamer tag.
Hope this helps!
Regards,
The Volunteer Moderator Team