If you are interested in this kind of work, there is a number to call. You call and tell them you are interested.
The next time they have a testing and interview session, they will call you to come in.
I had my testing and interview session yesterday. It's important to get there early. Get there before the designated time. You want to be first in line to sign in. Interviews are done in the order that people sign in. If you sign in early, you should be able to complete the process in half a day.
The first task is the skills test. You must pass the skills test. The test is pretty easy, in my opinion. Basic math, vocabulary, and map reading. It's pass/fail and they don't tell you your score. High scores don't seem to help. The only thing that matters is that you pass. The interview is the important thing.
On to the interview. There are two parts to the interview, a simulation of the job tasks, followed by a structured behavioral interview.
The simulated job task involves reading a series of survey questions, the same kind of questions you would read when visiting a residence to gather information. If you can read aloud, you should do well on this part of the interview.
The second part of the interview was some fairly standard interview questions. I hated it, but I am terrible in job interviews. If you do fairly well in most interviews, you should do alright.