The windows are all peel-n-stick, from the framing to the "glass". Before removing the window frames from the sprue, I spray-painted them with a rusty-red color. Each window frame consists of three parts. The larger part, shown at the bottom of the photo, goes on the outside of the window. The middle part is then attached to it from behind, and the upper part is attached to the bottom half of the middle part. It is confusing at first, but once you've done one, the others and the doors are easy to do.
The kit's instructions state to assemble the three window frame parts as one unit and then install that assembly onto to the building. My thinking was that the odds of getting that all perfectly straight were slim. So, my approach was to install each part separately to the building. The first one is the larger exterior part. I used a square to align the part such that it sat centered on the window opening. While holding the square in position, with my other hand I removed the paper backing of the peel-n-stick window frame part. This is a bit tricky, but with practice it is doable. Then using a pair of tweezers, I carefully positioned the part up against the square, while making sure it was centered across the opening. This is definitely the hardest step of doing the windows.
This is what it looks like from the interior of the building when the exterior part is installed. The adhesive of the part is now exposed and ready for the next part.
The middle part is then attached to the back of the exterior part from the inside. This guarantees that it fits in the window opening and that is sits square to the exterior part. After removing its paper backing, you can then apply the third part to the bottom half of the window. Note that this photo is taken with the window upside-down (i.e. the photo was taken from the top of the building looking down). Remove the paper backing from the third part as well, because the window "glass" is next.
I decided to leave the paper backing on the window "glass" in place. The plus side of this approach is that the clear plastic is protected from scratches and fingerprints. The downside is that it is a bit of a challenge to remove afterwards.
The paper backing on this glass is hard to remove. The way I did it was to use a knife to get the corner started, and then use a pair of tweezers to carefully remove it. It tears, so you have to do it a few times. Not difficult; just tedious.
All of the upper floor's glass has been installed. You might also note that I am building this on a sheet of glass. I have four rubber feet on the bottom of the glass to keep it from sliding on my workbench. Under the glass, I have placed the current instructions page, so that it remains visible at all times, while also being protected and out of the way.
Before working on the exterior trim pieces, I taped a sheet of sandpaper to the glass plate that I use as my work surface, and I then sanded the top and bottom of the structure such that any unevennesses were removed.
Using the glass plate, I was able to apply the peel-n-stick bottom trim pieces. I found the bottom trim pieces not long enough to cover the entire lengths of the structure's walls. I will hide that with some scenery later on. The one by the lower door is particular important as the door's trim piece will need to fit into it later on.
The exterior trim pieces were a bit of a challenge to install correctly, because they need to be straight, of course. Pay attention to the instructions to know which one "overlaps" the other.
Next up are the two doors. I did the doors the same way I did the windows. First I lined up the exterior door frame on the lower door.
The two parts of the door are applied one at a time to the inside of the door frame of the walls. That lines them up perfectly with the exterior door frame.
The frame of the second floor door has be positioned such that it clears the second floor landing. I temporarily placed that part in its slot in the wall (no glue), and positioned the door frame accordingly, as shown in the photo. One thing to note here, which caused me some extra work later, is that the landing actually consists of two pieces, which I had not realized at the time I was doing this step, so my door frame wound up sitting a bit too low.