If you want to make someone a follower, follow these steps:

1. Make the NPC and place him ingame as the tutorial tells you to do: http://www.creationkit.com/Bethesda_Tutorial_Creating_an_Actor

2. When you are done, go to the 'Factions' tab

3. Right-click in the table found there. A menu will drop down. Press 'New'

4. Another window opens up. Search for CurrentFollowerFaction. When found, select it and press OK. If done correctly, the faction is added to the list.

5. Now click twice (not doubleclick, just 2 slow clicks) on the number in front of CurrentFollowerFaction, in the Rank column. Set this number to -1.

6. Repeat step 3, but now you search for PotentialFollowerFaction. Select it and press OK. The rank number stays 0.

7. Now go to the 'Relationships' tab and right-click in the table. Press new. Another window opens.

8. Do the following things:
* Type a fancy name in ID.
* Leave ParentNPC untouched.
* Turn the field ChildNPC into 'Player'
* Turn RelationShipLevel into 'Ally'.
* Press OK

Now save your plugin and test it in your game.
I hope I explained it correctly. If not, ask away.