Well, you definitely should not create a new table (or more) for each user.
You need 3 tables in general.
First, a table for users, `users`. With columns: id, name ... and whatever else.
Second, you need a table for channels, lets call it `channels`. It will have two columns: id, name.
The third table, lets call it `channel_watch`, will have columns: id, user_id, channel_id, watch_time
Now, when you add a user, add the row to the users table.
When you add a user watch, check, if channel exists in channels table, if it does, grab its `id` if not, add a row and then fetch the `id` column value of the inserted row.
And finally, insert one row to `channel_watch` table with known user_id, channel_id and the time of the show.
All the ID columns are usually AUTO_INCREMENT, so they are generated automatically when new record inserted.
Also, reading a book on relational databases will not hurt.