Not looking at size (I know this should come down longer and be half the width of the window) and color (I want dark brown but not sure which color) how does this style fit my window? Should I add a little wood trim to the top?

Good lookin' house! I would go for a dark almost black navy blue, same hue family as the body. Because it would be the more edited, simpler choice. Edit and simplify is always a good plan IMO. Never use oil based for anything. It's especially a poor choice for exterior because it doesn't have the same flex and resiliency as water born paints. It's not flexible, doesn't expand and contract with vacillating temps and it cracks. No need for FPE unless you really want to try it. Ben Moore's top tier exterior is more than adequate for shutters.

What color is your roof? And what colors are in the brick? Since you have board and batten siding on the right, I would think that taking down the shutters would be okay (they're not the right size, anyway). I wouldn't paint the garage a different color - paint is the same color as the body of the house, so it doesn't stand out. I think a darker color would look great, but I prefer dark and bold. I would try and pick a color that's close to the darkest color in the brick and paint the trim in that, then use a color that's a few shades lighter than that for the body. This isn't a photo of a rancher, but gives you an idea of what I mean about the darker trim:

@Patricia Colwell, I included a link to the shutters in my post but left out pictures of the house and shutters because my question pertained to a method for hanging the shutters. I don't think there's a special circumstance or a design issue, just some help for some reluctant and unexpected DIY-ers. Here is the "after" picture that another Houzz user created for us that we've been using as a guide for our refresh project. Our house now looks essentially like the picture below now that the painting and new roof are done, but we went went a different color for the shutters and the front door. Our new shutters are half the width of the windows, and we are adding faux hardware to make them look operable. The shutters have no holes or hardware and didn't come with hardware to install them, which is why I'm reaching out to the Houzz community to ask about installation methods. Here are views of the shutters taken as screenshots from where we bought them: