Go to your Add-Ons folder
This should be C:\Users\[your username]\Documents\Add-Ons unless you chose another directory during installation
See the files here? These are decals (the ones you put on the front of your player's body). Some people have mods so don't panic if you don't see the exact same files as in the image
Right click them, click "Copy", then...
Go to C:\Program Files (86)\Steam\steamapps\common\Blockland\Add-ons. Click on OS (C:), find Program Files (x86) and so on. Refer to the above picture as needed :)
After you're done with that, do the same to the faces
And you're done :)
This is just assuming you have Windows. If you're a mac user I can't help you there