I’d find a good YouTube Channel like Makers Muse or Make With Layers for some beginner tips and tricks, that really helped me when I was starting out to get into the lingo.
As for software suggestions. Follow the recommendations from the manufacturer for the printer for software. Using Printables or Thingiverse for models to start with. At least to get started.
Then understand what printer you have. There is a world of difference between an Flashforge Adventure, Ender 3, and Prusa Mini.
After printing some fun models like a Benchy, try making your own stuff you’ll have a good feel for what’s a good print once you’ve printed other models, and have a few failures.
My software recommendations are as follows:
Modelling software for the teen: TinkerCAD, it’s free, it’s simple, and there are hundreds of tutorials going over how to use it. The software feels limiting for the experienced, but for a newbie it’s not bad
Next steps: Google Sketchup is another free software, still limited but has a lot of resources and is a good intro into cad.
For you: Fusion360, I think it’s still free, but with heavy restrictions. But from the last I checked it still has all the tools you need to get started. Plus it’s well documented with dozens of tutorials and guides.
My Software: I use to use Fusion, but I moved to FreeCAD. Made with layers goes over why this isn’t the best software and it’s many many issues. But for me I personally love using it with the sheer precision and control I can get with my designs. It’s not for beginners and the documentation is poor, with virtually no tutorials. I’ve done a small write up for how to get started before so check my comments if you are interested.
Otherwise Cura or PrusaSlicer is to get your models to print.