The catalog page within your theme will list all of the visible products currently on your store.  This page will have the URL - your-store.com/collections/all.  By default, the products which appear on this page will be sorted in alphabetical order.  However - you can create a collection to control the order in which these products are displayed.  

Step 1: Create a New Collection

1. From your Shopify admin, go to Products > Collections.

2. Click Create collection.

3. Create the collection:

   1. Give your collection the title All.
   2. In the Collection type section, select Automated.
   3. Set the product condition Price is greater than $0.
   4. Optional: To hide products that are out of stock, add the condition Inventory stock is greater than 0 as well.

4. Click Save.

Step 2: Sort the Collection

Now that you have created your All collection, you can sort the products within it.

1. Scroll to the Products section.
2. Select an option from the Sort drop-down menu.

If you select Manually, then you can rearrange your products by using their drag and drop handles ⋮⋮.

Step 3: Rename the Collection (Optional)

If you want to change the title of your All collection, then you can edit it now that the collection has been created, under Page title. It is important, however, that the handle of the collection remains set as all. You can confirm this:

1. Scroll to the Search engine listing preview section.
2. Click Edit website SEO, and in the URL and handle text box, you should see a URL that ends in /all.
3. If the URL ends in something different, then change it to /all, and click Save.

The above steps have been adapted from Shopify's guide, Change your catalog page.