So this is a product.
The text you see here is a Product Description. Every product has a price, a weight, a picture and a description. To edit the description of this product or to create a new product you can go to the Products Tab of the administration menu.
Once you have mastered the creation and editing of products you will want your products to show up on your Shopify site. There is a two step process to do this.
First you need to add your products to a Collection. A Collection is an easy way to group products together. If you go to the Collections Tab of the administration menu you can begin creating collections and adding products to them.
Second you'll need to create a link from your shop's navigation menu to your Collections. You can do this by going to the Navigations Tab of the administration menu and clicking on "Add a link".
Good luck with your shop!