Ah yes, thank you very much for your help !

no problem - the tutorial doesn't touch on this, but when you go to the blueprints menu (U key, or blueprints on the left icon bar) and load, at the top of the screen where you choose a blueprint to load there are two sets of buttons. Top left is ship, station, and module, but in the top right there should be an option for default and custom.
Every blueprint you subscribe to or make yourself get saved under the custom library.

How do you find the blueprints ingame after subscribing? I can only find blueprints already added by default, none from mods I suscribed to... please help a new player :)