Here I have tacked the door sills for the pilot and passenger. There are a couple of important things to keep in mind; first, the forward part of the sill needs to be level. This will someday be the reference for leveling the aircraft when you do you weight and balance.
Second, the doors bow out a little bit, so you need to ensure that both sides are the same distance from the centerline.
I made a quick jig to ensure I got the forward part of the sill level (picture 1). I also made sure that the jig allowed the door sill to bend out the requried distance.
Once I had made the sill itself (including the proper bend), I cut and trimmed the sill to fit in the opening and tacked it in (pictures 2 and 3).