Hey Slotzky welcome here in our great community !
A good start is the tutorials, you can find them
https://www.thenew8bitheroes.com/learn
I suggest:
- The orientation video, just to learn how to use the tool (don't follow the tutorial about the game, nesmaker has changed since)
- All the "intermediate" tutorial videos (for each module / type of game)
- And if you feel at ease, you can follow the "Advanced" ones.
Then, you 're ready to try making your own.
On the forum you will find a lot of resource, fixes, scripts, answers to your questions...
Feel free to ask, comments, share your projects.
Have fun!