Hi! I'm asexual too! You're not alone and I'm glad you exist! :)
When I came out to my family and friends, it was a bit... anti-climatic.
"Hey, uh... I need to talk to you. Sitting down? Cool. So... first off, thank you for loving me. I've noticed something about myself I'd like to share with you, because I really want to be Known. I'm Asexual."
Only one person knew what an asexual was - the rest, I just had to explain. "Here's the technical term for Asexual, and here's what it means in my life." So be prepared to explain what Asexuality means to you.
I've gotten several responses.
That's it, end of story, nothing scary. Explained, accepted, moved on. :)
2. "You just haven't found the right person yet..."
Don't get angry at this one - the person saying it (probably) isn't trying to invalidate you. They're probably thinking, "Oh! Sex makes me happy! I want them to be happy! I'll tell them they'll want happy sex later!" Granted, that isn't how asexuality works (necessarily), but just know that this response is probably them trying to share their form of happiness with you.
I accept this response as (albeit misguided) kindness and reply: "Ha ha... maybe... until then, this is who I am, and I just wanted you to know."
3. "...so... you're a closet gay/bi?"
To which I reply: "Nope, sorry - it's different. I love you/my family/my friends, but I don't really care for the sex thing, either direction."
If you're doing this in person, and you have fun friends who won't make (too much ;) fun of you for it... a metaphor I've found is Soda and a Glass.
Holds up soda. "This soda represents love. We're all human, right? We all want love?" Opens soda. Holds up glass. "This glass is sex. Well, Sexual people like to drink the soda out of the glass. They feel love through sex." Pours soda in glass, hands to Sexual friend. "On the other hand, as an Asexual, I just want the love, no glass required." Sips soda straight out of the bottle. "We're both getting the love we need, I just enjoy it simply, whereas you prefer the extra step," taps their glass, "of sex. Neither's better or worse - we just enjoy love in different ways."
There's a lot of other awesome Asexual explanations you can Google. It's a really simple thing, but nobody talks about it, so it might take a minute to sink in.
Until then! Be patient. Don't assume the worst - if they truly love you now, they'll love you after you come out. They might just need a little time to wrap their brain around it.
Also, be patient with yourself. Don't do anything if you feel it's unsafe or if you aren't ready.
Best of luck and may you feel peace! :)