For example, take Harry Potter. It’s fairly evident from examining the text that the ability to do magic is a dominant gene, but Rowling never bothers to tell us because it’s really not important to the plot at all.

Conversely, however, readers can and will spot inconsistencies in your magic system even if you don’t explain the rules. Therefore, you should know what the rules are, and stick to them – even if you never tell people what those rules are straight out.

You can develop your magic system as much as you want in your planning and notes. You alone can develop your rules and source of power for your own reference. You can know it inside out and back to front – if you’re familiar with how J.K. Rowling works, she has tonnes of stuff the public has never seen and probably never will see. Because she’s planned out everything, if she’s asked about how a particular aspect works, she has an informative answer.

If you write about the magic as if it’s "the way it is" with confidence – which will come through knowing exactly how everything works – it’ll come across to your readers in your writing and tone. Simple explanations if they’re really needed always work best. An information overload makes readers doze off.

Good luck, you sound promising.

Readers will understand it easily enough if you explain it. But in simple terms that don’t take too long.