Open YouTube and sign in to your account
Find the channel or comment by the person you want to block
Click the channel name or profile picture to open their channel
Select the flag icon (Report) next to their channel name
Choose Block user
Confirm by selecting Block when prompted
If blocking from a comment: locate the comment
Click the three dots (More) next to the comment
Select Block user
Confirm by selecting Block when prompted
To manage blocked users: open YouTube Settings
Go to Privacy
Select Blocked users
Review the list and unblock if needed