Step 1: Download RTB
here.
Step 2: Save it to your Blockland Add-Ons Folder, usually in C:/Program Files/Blockland/Add-Ons.
Step 3: Open up Blockland, and go to "Start a game".
Step 4: Click on the "Colorset Manager" button (or something like that), find the colorset, click it and click "Load".
Step 5: You're done.