The proper way to say "I love you" in Spanish us "Te Amo". If you want to say 'I love you' in Spanish the proper way would be 'Te Amo' . This phrase is usually used when a person is professing romantic love to another person. There is another phrase that also basically means "I love you" that is actually used much more often in all types of situations instead of just romantic love.
This phrase is "Te Quiero" and in a literal sense this phrase translates to "I want you." Whereas "Te Amo" is used only in romantic love this phrase can be used with family members, pets, friends, or also signifcant others.