When viewing a collection, or the homepage of your store (which by default displays the 'Home' collection), you are able to control the order of the products by sorting the products within that particular collection. Let's take the example of the Home collection. Firstly, go to your Collections section within your back office, and click to edit the Home collection.
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From here, you'll see a 'double-arrow' arrow to the left of each product in the collection. By clicking down and holding on the 'double-arrow' icon, you can drag a particular product up or down to change it's position in the collection. Upon making your changes, be sure to click 'Save changes' and you'll then see your changes applied on the front end. Please see this annotated screenshot:
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