There are great resources for getting started with Scoutbook. A list of some of them are linked to here: Caution ⚠️ tags on everyone - #15 by CharleyHamilton
but there are tons available at https://help.scoutbook.scouting.org
I would recommend starting there to get an understanding of how Scoutbook works.
Your unit leadership (e.g. den leader, cubmaster or scoutmaster, committee chair) should be able to provide you with your scout’s BSA ID number, and may be able to identify whether or not you already have a parent account in Scoutbook that is connected to your scout.
