You first have to have been on the order list for 6 Months. After that, I would say, just ask.
I would write them about:
- your particular situation, background, projects, career. They want a broad range of testers, so help them find you!
- why you want to test TextBlade, as opposed to waiting for others to find all the bugs. Many of us are early adopters of certain things and late adopters of other things (right now, self driving seem scary to me).
- if you have testing experience. It won’t work against you if you don’t. I think the common traits are, awareness, honest/candid/accurate/detailed feedback, patience, and common sense (i.e. don’t tell them you plan to use TextBlade on the inaugural manned SpaceX flight, with the flight computer, and no backup keyboard).
- about your setup, which computers and devices you use m, what keyboards you use, and the situations you use them in. Some interesting finds came from people using TextBlade on a submarine (steel work surface).