Hi,
Extract everything into your trackmania folder (example:C:\Users\yourusername\Documents\Trackmania\items ).
If you want my macroblocks library (Spaceships, Plane, Train, Bridge, Portals...) you can download it here :D https://drive.google.com/file/d/1P29rbOZovNF1kZTEGulkm_Ma_LtNcZUS/view?usp=sharing
I can't share it on itemexchange cause some blocks are already uploaded and I dont' want to do a list of which block of which pack you need. So everything you need is in this zip file.
Have fun.
Tatsne.