I got my first camera when I was 21 - my boyfriend gave it to me for my birthday - but at that point politics was my life, and I viewed the camera as a tool for expressing my political beliefs rather than as an art medium.

This quote means that when the person in the quote was 21, their partner gave them a camera for their birthday. Instead of looking at the camera as a way to create art, the person thought of it as an extension of their political beliefs. They were more focused on politics than art at the time, so the camera was seen as a tool to communicate their thoughts and values about politics.