Have you made your entity file and created the pertinent table in your setup file and local database?
If so, you can create entities like this (assuming you're in a controller):
$entity = $this->em()->create('Vendor\AddOn:Entity');
Then you can assign the values from your form input:
$entity->column = $value;
And finally save the entity to the database:
$entity->save();
It wouldn't be a bad idea to encapsulate the creation process in a service if there is anything more complex than that going on, or maybe a
FormAction
at the very least, but the above will work for starters. If you need help with more fundamental aspects (fetching input from the controller, creating entities and tables, etc) I'd recommend having a look at the
tutorial. Otherwise if you have specific questions feel free to ask.