If you're going to be in Edinburgh for a few days, you'll have a greater range of choice in accessing cell shops there. The staff at your hotel can provide information on the nearest one. It would be a good idea to verify that the phone is indeed unlocked, as it won't work with other SIM cards unless it is.
The staff at the cell phone shop will be able to provide some information on how to use the phone.
You'll likely have several different plans to choose from, so you'll have to give some thought on how much you'll be using voice, text or data. You'll also need to be clear on the method for "topping up" the card when your time is depleted.
This chart may help with the method for making calls in Europe.....