Instructions
Construct an object using the game's included tools, such as blocks, the wrench and the spray paint. The object can be anything you like: a vehicle, a weapon, an appliance or a building. When you're done, save it.
Navigate into your computer's "Program Files" folder, then open the "Blockland" folder. Locate the file you saved inside the "Base" folder, including any sound or other non-standard files it may have used. For instance, if you also made a "whoompa" sound and used it for your object, then you will also need to find the "whoompa" file.
Copy the files for your add-on to a separate folder on your desktop. Do not include thumbs.db files or .ogg sound files. Do not copy any existing files that come with the game.
Right-click on the file folder and select "Send to --> Compressed (zipped) folder."
Navigate back to the "Blockland" folder in "Program Files." Move your zipped folder to the "Add-ons" folder. Do not extract the files. You can also upload your zipped folder to forums or send it to friends.