How do you say l Love you in Latin?

It depends what part of speech you mean. As a noun ("I believe in love"), it would be amor. On the other hand, the verb "to love" is amare. If you meant something like "my love" as a form of address, it would be different again, and I'm not sure what it would be.

Keep in mind that Latin Words change their endings. It would be easier to give a precise answer if you gave the Word in context, but my guess is that you are looking for the amor sense.