invalid credentials

hey guys, idk if this is gonna help u guys out but i had a problem login at first it would always say invalid credentials and i couldnt find any help, i read the credential guide and it didn't help me. i figured out that the username it was askin for, was the one u first created a account on ur conputer. for exemple my mom gave me her computer and when i got it i changed the account name to mine instead of hers, but i had to login with the old account name on my phone to connect to my pc.. idk if that helps, sry for the bad english too