Larry has the best answer here.

You just have to start somewhere doing something.

Actually, I learned a lot when I worked for an A/V chain and was HQ's rep on the job. I had to be there; I knew lots about what they wanted the store to look like; I had enough sense to put the front door in the front; and I had LOTS of time to watch and see how the building was put together.

This "how it is put together" has been the skill I use every day in installing. Like the time I had to run a wire about three feet down a wall. I could run it about 30" down from a hole in the wall, and I could run it about 30" up, but I could not run it the whole way. Why? This was a 1930s house with 2x4 supports running down the wall at a steep angle, and one was pushing my wire sideways! I had SEEN that type of support before, and that made me able to figure it out.