someone talk me through finding high volume low competition keywords?

Honestly the high volume part is usually the trap. Truly high volume and truly low competition almost never sit on the same keyword, because everyone runs the same filter in the same tools. What works better for a small team: go after mid and low volume long-tail terms that are tightly on topic for the client, and judge competition by looking at the actual SERP rather than the difficulty score. If page one has forum threads, thin listicles or pages that don't really answer the query, you can beat it. If it's all strong brands with dedicated pages, move on. Twenty of those that you can actually win add up to more traffic than one big term you sit on page three for.