Cal here from Shopify, thanks for reaching out to us. Welcome to Shopify! It sounds like this is your first business with us, which is super exciting. There are some questions I'd like to ask in order to best assist with this query, so I hope you don't mind!
For most new merchants, the first port of call is the introductory guides. Once you read through them and put them into practice in your store, you'll understand the basics of the admin and how to get started selling.
I'd also suggest looking at our fantastic courses over on Shopify Compass for a more in-depth look at how to take your business from set up to the first sale!