prove oneself as

prove (oneself) as (something)

To do what is necessary to convince others of one's skill, capability, or authenticity in some role. Young men of the tribe are required to prove themselves as hunters before they can assume positions of leadership in the community. They've given me a few freelance projects to prove myself as a copy editor before they agree to hire me on a permanent basis.
See also: prove

prove oneself as something

to demonstrate that one can serve in a certain office or capacity. It's time to promote her. She has proved herself as a teller. I proved myself as an investor by making a lot of money in the stock market.
See also: prove