Hi @Edenessentials! Thanks for reaching out! The best way to do this is to go to Locations in your Square Dashboard (under Account & Settings), select a location, and scroll down until you see "Match Item Library from Another Location." Make sure to match it to your main location that has all the inventory and then click "save."
If you have specific items that you want available at all locations, you will need to select each item and mark it available at all locations.
Let me know if you have any other questions. 🙂