Hey, happy news!
I'm actually not that experienced in what you're asking about, being a bit the shy type myself, but let me sort of share what worked for me recently. I said "Hey, I had a lot of fun with you this weekend and I found that I like you more than I anticipated I would. If you aren't opposed to the idea, I'd like to continue seeing you and see where it goes." Only, I ended up doing it via PM for various reasons and had a lot time to compose exactly what I wanted to say (twice, as it happened, but that's another story) and it was quite a bit longer. You could try taking that sentiment, though, and rewording it so it doesn't sound like you're reading a cue card and has a more natural "speaking" flow to it.
EDIT: Or you could take ^'s advice which is much simpler than mine.