I followed the instructions for drilling the door-bottom guides.
There are two door stops to the right of the doors.
And two more to the left of the doors. I had a bit of a challenge drilling these, as the block to drill into is quite small.
The 3D-printed parts that are the doors' guides and stops are different in their shapes. You get two of these strips, one for each side of the car. You get one extra guide and extra stop, just in case you drop one of these tiny parts and it disappears "forever". I used a sprue cutter to carefully snip these off. For the door stops, I kept the attachment barrel/sprue short, as it was hard to drill deep holes in the door-stop locations. The holes for the guides can be drilled as deep as you want, so you can cut these off as close to the base as desired.
The door guides are shaped like the letter "L", and they need to be oriented so that they are pointing up. The door guides to the right and the left of the door frame will not fit without modification. I carefully snipped off the right or left edge of the part to get them to fit up against the frame. I put a tiny amount of superglue into the hole, and then used a pair of tweezers to insert the part. I then tweaked its orientation so that it was as straight as possible; you'll have a few seconds before the glue grabs.
The door stops are shaped like a straightened-out letter "Z". The upper part needs to point toward the door. If the hole is deep enough and the stub is short enough, these are easy to install in a similar manner by putting a tiny amount of superglue in the hole first, and then orienting it such that it is horizontally straight.
The same thing goes for the door stops on the left, having their upper part also pointing toward the doors.