Cal here from Shopify, thanks for reaching out to us. Firstly, welcome to the platform! We are delighted to have you.
In response to your query, you can find your published theme at any time by going to Online Store in your store admin:
Which theme have you decided to use for your business? Have you played around with a few different free Shopify themes? What products were you hoping to sell (as some themes suit specific product niches better than others)?
If you're entirely new to Shopify, I also always recommend having the introductory guide bookmarked to help you along the way, it's a fantastic source of information when you're getting your store set up!