Where should I enter my Simbrief information?
In the EFB.
Can I enter my Simbrief information in the MCDU?
No.
What information should I enter Simbrief username or Simbrief Pilot ID?
Simbrief Pilot ID.
I used to use Simbrief Username.
Yes, but it doesn’t work anymore. Only Simbrief Pilot ID.
I use Xbox, and when I use the Xbox on-screen keyboard to enter my Simbrief Pilot ID, it doesn’t work.
That’s correct (or a bug), you must activate the EFB virtual keyboard and use only that one.
I entered my Simbrief Pilot ID, but it still doesn’t bring up the Simbrief information.
Yes, after entering the information for the first time, you must exit the simulator and re-enter for it to correctly take the changes.