All you have to do is right click your shortcut for BL and do the following:
Right click your Blockland shortcut. (Durr)
Click properties
Look at the target
It should say something similar to this:
C:\Blockland\Blockland.exe
(It might be C:\Program Files\Blockland\Blockland.exe it's just where you installed it too)
Now, add this to the end
C:\Blockland\Blockland.exe -mod editor
Your good!
*Press F10 to work in - game*
EDIT: Oh, fail. That's a better one. Disregard mine.