Wow.
Just...wow.
Step by step instructions on how to download add-ons:
Step 1: Click the download link provided by the topic poster.
Step 2: Save the file to your Blockland Add-ons folder. If you aren't prompted where to save, simply move the file from where it was downloaded into your Blockland Add-ons folder.
Step 3: Run Blockland.
Step 4: Click "Start Game"
Step 5: Click the Add-ons tab, and enable the add-on you downloaded.
Step 6: Start you game.