For me it was by watching Junjou Romantica in Youtube when I was 16. I mistook Misaki with a girl and I thought it was shoujo. So, it was a real shock for me, I didn't even know yaoi existed in general and I was super innocent even at that age. Anyways, at first I felt disgusted (I grew up in a quite homophibic family), but after that shock I became curious and kept watching. Now I only read yaoi lol.
I think in 2017 I watched my first yaoi, it was junjuo romantica. I was like uhhhh what is this, seems interesting and then I watched it 3 times and was looking for newer/better yaoi. That's how I ended here, on webtoon and manganelo(づ ̄ ³ ̄)づ reply