New windows were put in about a year ago and we were left with the result shown in the photos. I'm tired of seeing this and want to fix and finish it myself. However, I'm not sure what steps to take.!
Get some 1x4. I'd go with primed fingerboard pine. Cut to size and install against the metal frame of the new window. Caulk, Paint.
I've installed windows and then completely hidden the window frame with interior trim such that you only see the trim I installed and the glass. The frame that holds the glass is hidden with the trim that butts up against it.