There were many steps.
My interest in feminism was sparked by Glynis Johns and the Sherman brothers. Quite how I got to from there to the real story of the suffragettes I was too young to remember, but that song was what started me on the trail of womens rights. (There was brief wobble in the early 90s, when the LibFems almost persuaded me that I was an 'equalitist' rather than a feminist, but then I hit the sexism of the world of work and got over it). It was a firmly empirical feminism - based on stats, data and experience. I didn't come.to the theoretical and philosophical side until later.
That came when I discovered a talkboard I'd been on for ages had a feminism thread. Under a disguised title, hidden in the 'books' section. I hung about on there for a bit, picking up a large to-read pile when I realised that in jumping from Wollstonecroft to Pankhursts to the present I'd missed a lot of background discussion.Then we started asking why we were hiding, and I decided it was ridiculous - so I started a thread with 'feminism' in the title in a more obvious part of the site. At which point I learnt the meaning of 'pile on', a significant chunk of posters left, and the whole moderation system had to be revamped to hold the site together.
The addition of gender criticism to my beliefs is shrouded in the mists of time. I had a fairly ungendered 70s upbringing at a progressive school, but at some point I assume I was told 'Girls don't ...' or 'Only boys do...' and my natural stubbornness was activated. So the idea of sex defining social role, or of it being defined by clothes or interests, was something I saw as ridiculous for decades before the concept of trans came into it. I became aware of gender criticism as a wider movement through Let Toys be Toys and Let Clothes Be Clothes.
Life got in the way and I wandered away from the feminism thread for a bit. Then I'm not quite sure of the order of events that followed - the pussy hat controversy, man Friday, the Green Party designating women as 'non-men', a pile of increasingly insane things popping up on Twitter - an accumulation of bizarre events that meant I went back to the feminsim thread to ask WTF? and discovered it been forcibly split in two, much like.the feminism board here. Discussion was rigorously coralled and policed - you'd all recognise the pattern of reporting, goading and drive-by scolders. But even that wasn't enough for the site owner, who had the mother and father of all mantrums and threatened to shut the whole thing down unless the vile transphobes were defenestrated. So (along with Elderberry, Sinner, duc and some others) I jumped before I was pushed. And landed here.