Depending upon the number of people, the context and the speaker, the words for "I want to be with you" in Spanish are:
Quiero estar con usted / ustedes / vosotros, as / vos.
But refering to "tú", one person, familiar style:
Quiero estar contigo.
There really is no direct way to use the term "wanna". You just have to use the full phrase "I want to".