I'm sure you have read alot of things with this topic, but this one really does work, its just that the people who make these topics aren't specific enough, this time i will be. Here's How:
1. On blockland forums find and install the Add-On
2. Move that Add-On to your blockland Add-Ons folder, but heres the problem: thers two of them.
3. make sure the file you install it to is C:\Blockland\Add-Ons\ and NOT C:\Program Files\Blockland\Add-Ons
Don't Understand? Heres a Video link: http://www.youtube.com/watch?v=7eioNK8cpWQ