You can say "Eu te amo." or "Eu amo você." P.S.: Just some tips in case you are curious: 1) In really few cases you can hear a Brazilian saying "Amo-te", like they usually say in Portugal. 2) NEVER say "Te amo." or "Eu lhe amo.", sometimes you can read these forms in Internet but they are wrong.

In brazilian portuguese , you can say it in two different ways -Eu amo você ( like nathally said) Or -Eu te amo.(where "Eu" is the personal pronoun and the subject of the sentence , "te" is the personal pronoun and the object of the sentence, and "amo" is the verb).

Eu amo você. Eu = Pronome Pessoal (in English: Personal Pronoun, "I", "Me") Amo = Verbo, "Amar" (in English: Verb, :To Love") Você = Pronome Pessoal (in English: Personal Pronoun, "You")