From the home screen on your Roku: Settings > System > About. The email address shown is the one associated with the Roku account to which your Roku is linked.
Using this email address as your login name, follow the instructions given you by @HDMIGuy .
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
If this post solves your problem please help others find this answer by clicking "Accept as Solution.".
Streaming Stick 4K+ 3821 | Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X