Ed Sheeran has a nice easy guitar style. “Thinking Out Loud” is in the key of D, which just happens to be a key we play rather well. Yay.
Some folks call the chord below a slash chord. I like to call it an inversion, since that is kinda what it is. Play the F# on the bass E string with your thumb.
Look at the Ensembles page for Tres Guitarras. This is also an option for the playing portion of your final.