WOTL - adding an extra row of units to your unit windows,
Anyone has a tutorial that will assist me accomplish this task?
If you are asking if you can expand the limit of characters you can have in your roster, then no, this is not possible at this time.
No one here hacks WotL, mostly only the PSX version, and even in that we haven't gotten a way to expand the roster other than
by getting rid of Guests (for Roster slots) and using those.