In order to formulate this phrase, start with the French verb for love, aimer.
The most famous of these are B euves de Comarchis, Ernaud de Girone, Garin d'Anseun, Aimer le chaff, so called from his long captivity with the Saracens.
Aimer is a regular, -er verb, which means that it is fairly easy to conjugate.
However, saying "I love you" in French is not as easy as inserting the pronouns on either side of the conjugated version of the verb aimer.
This would produce the phrase: "Je tu aime," but there is another problem with this phrase, which is that because the pronoun tu ends with a vowel and the verb aimer starts with a vowel, the pronoun tu elides with the verb.