What kind of printer is it? The more-experienced-than-me folks will probably be able to point you in the direction of specific resources depending what type of printing you’ll be doing.
When we first got into printing I taught my husband the basics of CAD with Fusion360, and after a bit of wrangling with the unintuitive controls he found it pretty easy to use. It’s free for personal use, which is the main draw, but also it makes it easy to share designs with each other. That said I’m sure someone will be along to recommend a FOSS alternative because this is Lemmy after all.
Mainly I just wanted to say welcome to the gang and have fun printing a load of stuff you didn’t even know you needed! :D