Is it on canvas or paper?
I would take it to a framer, they often have great suggestions and will show you different corners of colors/sizes frames so you can see before committing.
Canvas. So painting on canvas or papers will be framed differently.
It would be easy. But I'd like to know more about it and then do it buy myself.
So if it's on canvas the artist removed the stretcher bars (or painted without) for ease of shipping. Now it can be put on stretcher bars first before framing. Order from an online art supply 2 pair to match the size of the art. Google a video on how to stretch and staple the canvas to the back of the stretcher bars. (https://www.youtube.com/watch?v=T-6UoUgfp9w)You don't stretch it as tight as you would a blank canvas that you are going to paint on because your canvas already has paint on it and you don't want it to pull the paint apart or crack. Hope this helps.