Not sure if you are thinking of ways to insert data into the database directly, without using Mendix, but if you are contemplating this, then be aware that Mendix creates it's own index-field on any new record. So 'manually' inserted records will have a different id and will not get recognized by Mendix and Mendix will think the database is corrupt.
In a microflow you can use the create activity to create an object from your domain model.
Here is the documentation for activities
https://docs.mendix.com/refguide/activities
and a link to the mendix learning paths