Good question! I am very far from being an expert, so I struggled with the same problem. Here are a few things I found helpful:
1) Find and follow tags that you know something about. I spent a fair bit of time on regression early on because it included a number of basic questions I could answer. I also discovered some more niche tags that were relatively neglected, implying either that the regulars here were not especially interested in them or were not experts in those topics. Answering (and editing) questions on these types of tags helps a lot of people.
2) Look up the 'unanswered' questions on these tags. Frequently, there are a number of old-ish questions that are quite deserving of an answer. Sometimes doing this can be a bit thankless, but answering old questions can draw attention to them. While doing this, you will want to familiarise yourself with the most upvoted questions on those tags. Some of the unwanted questions will be duplicates, so you will help the community more by flagging them as duplicates rather than answering them.
3) Look up the 'new' questions on the front page when you visit the site, not just the home page (which also includes questions that were just answered, edited or bumped). Also look up the new questions of the tags you are interested in.
4) To make sure this does not end up feeling like a slog, pick a strategy that amuses you. Look up the CV badges and pursue any that you'd like, if that floats your boat.
5) There's a bit of disagreement about whether we should answer every basic question that gets posted. Some people prefer to stick to CV's original goal of maintaining a corpus of high-quality Q&As, others are happy to answer basic questions, most fall somewhere in the middle. In case you fall into the second group, you will find it easier to identify questions to answer. But be aware that these questions end up getting closed more frequently than others, either as duplicates or as lacking in important detail.
6) When you open any question, CV lists a bunch of 'Related questions' on the right side of the page. So when you find one question you are able to answer, it can frequently lead to discovering a few more.
And if you have not seen it yet, this is a very useful thread about how one can help here even without the advanced training that you clearly possess: What is the best way to give back to the community when I don't have the math skills?