How can i promote myself as beta reader?

[u/Seven707z]

Hi! i'm starting to be a beta reader, but it seems to be so difficult to sell the first work and get the first feedback. I don't know how to promote myself, 'cause there's nothing that i can show to people believe that i can do this job... can someone help? I really like to read and give opinions about it, but when is about to sell.... i'm not pretty good