Hello,
I'm looking for help with my new windows I just installed.
The question is about exterior trimming. I don't know what to do next and how to trim my windows to make it look nice.
I'm thinking about vinyl trim.
There is cedar siding on my house.
I'm looking for options I have as well as suggestions and instruction for DIY.

I see a thick vinyl trim is out that I know nothing about - looks expensive (the usual vinyl for putting on top of vinal siding is thin). You need something you can run on a table saw so that you aren't custom fitting shingles around the sides except on those two windows. There are MDO pre-painted trims that are cheaper, I think.
Calk around the edges of the flanges and also around the outer edges of the trim after it's in. I guess you don't need a top drip edge under that overhang.

This is a bit late but you first need to install weather tape over the flange. Bottom first, sides and then top. You can buy grain textured PVC trimto finish off. Looks like cedar. You can also use Hardie trim which is what most new homes use.

Remove cut shingles, weather tape window flange( can also use tar paper) and finish with siding(no trim). Nice clean look>

Chuck

Remove cut shingles, weather tape window flange( can also use tar paper) and finish with siding(no trim). Nice clean look>

Chuck

Good idea, however, the siding is too tick because it has some kind of isolation under shingles.

I'm trimming the windows anyway.

I checked out the 'cellular vinyl' trim yesterday. Very nice, although expensive. I think it's worth it.