If you want to just make a map
1. Download Mission Editor off the main site
2. Extract it.
3. Right click the BLOCKLAND shortcut
4. Select Properties
5. Something should say "C:\Program Files\Blockland\Blockland.exe"
6. Change it to say "C:\Program Files\Blockland\Blockland.exe" -mod editor
7. Open Blockland
8. Click 'Start Game'
9. Find a map to edit (Preferably not someone elses they worked on, use something like Flatlands)
10. ???
11. Profit
If you wanted to convert, ask someone else. Enjoy.