Better to let it happen naturally (as in they borrow your phone or something and see a pic) than to bring it up. Unless for some reason you have an urge to let it out. If they aren't into anime or anime-like games I wouldn't bring it up tbh. At least ppl who are into that stuff are aware of it so they are less likely to go "wtf?!"
Your best option is to hide it. Let them discover it. If you barge in your friends and say "I'm a rotten girl who loves male on male romances" I bet they're gonna go WTF. But if you think your friends is open-minded about it, then it's fine. Also, in the case that you have been shipping your male friends, HOLY MOTHERFUCKING HELL DON'T FUCKING TELL THEM! IT WILL NOT ONLY RUIN YOUR FRIENDSHIP BUT IT CAN ALSO RUIN THEIR FRIENDSHIP (OR IMPROVE THEIR RELATIONSHIP. WHO KNOWS HAHAHA)!
I've been a closet fujoshi for 2 years now. Ever since I've read my first BL manga (Honto Yajuu), I have been fascinated by male on male romances. Yaoi became a regular part of my daily life. I have a couple of friends but they didn't know I'm a fujoshi. Whenever my male friends become touchy-feely with each other, I loose my cool. It's like i'm in a Yaoi Wonderland. Is it okay for me to confess to my friends that I'm a fujoshi? I feel like if i did, most of my male friends will be cautious when they are around me. Worst case, they will stop hanging out with me... ╥﹏╥