Here is an approach to make a macro that will use an item in your equipment inventory. In my case, I have a Ring of Spell Storing in which I keep 5 level 1 uses of Hellish Rebuke. I have the uses set to 5/5 on manual reset. To make the macro, open your character sheet and click the ring. It will consume a use and put the description in chat. Now, click in the chat box as if you were going to type and click the up arrow. That will produce the code you need to cut and paste into your macro. Do that and save the macro. Check the box to add it as an action. Done.
