How do I tell my boyfriend??

i'd suggest you lie down and very seductively ask him to come with your finger and while you do so tell him that there is something very big (or any other word of your choice) and exited under your underwear. and he will wonder what is it.

i think it is a very sexy way to introduce it, as it will make him more aroused with the introduction and the temptation of finding out and so very smoothly he will love it.

really good luck.

I hope I'm not late in replying, but I feel I'd love it if you told me that "I'm excited and wet inside, that my outer features are engorged, ready to be eaten!". I wouldn't love the word big or large as introductory.

Take his hand and guide him to touch you first. Don't be afraid to tell him if something feels good to you. For me, I like it when my wife tells me "that feels good" or "I love your tongue".