SO important! Indie creators of every kind need to understand that their content - not the platform it's on - is their biggest asset worth protecting.
I'll add:
1. Learn a bit about copyright & make sure you have a 'default' license for your work
2. Read & understand the EULA of any platform you post your content on - many of them wind up taking over rights for anything you post!
3. BACKUP YOUR DATA! At least two places, and at least one should be a physical drive that lives with you.