Are your reviews posted on the site with the same email address you use for the forum?
If so, all you need to do is pop your name down when a new tester topic is posted 
Make sure you’re stating which item/s you’re interested in testing, saying “all” or “any” will get you nowhere 
You’re more likely to be selected for things similar to those you’ve already reviewed rather than something completely different.
If you have any items that you’ve bought elsewhere but LH stock, you can still review those 
Probably the most important thing is to have patience - keep popping your name down. There are a LOT more people wanting to be testers than there are opportunities available, so don’t be disappointed if you don’t get selected.
Brenna takes a variety of things into account when choosing who to send testers to, and every now and then she will have time to give advice on reviews and how to enhance your chances of getting chosen.
There’s the Sex Toy Tester - Chit-Chat thread as well which can be handy.
There’s also a topic here where you can post your reviews and experienced testers can give feedback to try and help with your chances (I can’t find the link right now, it’s 5am and I should be asleep - sorry 
)
I hope that helps 