In phpMyAdmin open the users table then on the right of the screen, at the top, there is a row of tabs "Browse, Structure, SQL, Search, Insert etc", click on Structure.
Now go to the bottom of the list and you will see a line that reads "Add 1 columns at....". The "end of table" should be selected as default but you can see that you can add as many columns as you like, wherever you like. Just leave it at the default ( 1 column at end of table) and click the "Go" button.
The next screen
Give the column a name "AccessLevel" but you can call it whatever you want (no spaces allowed)
Leave the "Type" at it's default of "INT". This means integer so it's expecting a number.
The next one "Length/Values" you need to enter a number. This is what I was talking about yesterday. You can put any number in here from 1 upwards. If you put a 1 it will expect only a single digit (1-9), 2 and it will accept 2 digits (10-99) and so on. What you will be placing in here is an access level so you need to think of how many access levels will I need. Probably no more than 9, most likely only 2 (user and admin), so just put a 1 in here (or whatever the video is telling you).
That's it, now just click on the "Save" button.
You can now return to the tutorial videos.