First time sex

So im 15 and my boyfriend is 17 and he has had sex once before with his ex. He has told me he is ready to have sex with me whenever I feel comfortable and want to (im a virgin). I don't know how to tell him. Some people have said that if I don't know how to tell him, then I am not ready. I know I am ready, I don't just wanna say "hey im ready for sex." I am not sure exactly how to start the conversation with him. Some advice and help would be awesome!