You have to make a Blockland folder in your Documents folder, and in there, extract
this pack of default bricks that were converted into the SPECIAL format and rename the 'Default Bricks' folder to 'BLS_Bricks'
If you have any import issues that mention textures that can't be found, create a base > data directory in the Blockland folder that's inside your Documents folder, then copy the 'shapes' folder from your game's actual location and paste it into the newly created base > data directory
Note that if your builds use a bunch of non-standard/default bricks, the importer may not be able to detect them