"I trust you."
Εμπιστεύομαι is "trust, whereas πιστεύω is "believe". Πιστεύω σε can be used with the meaning of "trust" the same way "believe in" does, with the same differences in meaning. So Πιστεύω σε 'σένα=i believe in you, σε εμπιστεύομαι=i trust you, πιστεύω στις νεράιδες=i believe in fairies (no "trust" meaning here), but εμπιστεύομαι τις νεράιδες=i trust the fairies.
Εμπιστευτώ is another form of the verb, just not the present in the indicative. It's used in simple future and aorist subjunctive. When unsure of such things, you can check a conjugation table. The team has provided a list of useful resources here MODERN GREEK RESOURCES How to get the keyboard and much more. that includes links for conjugations - I usually link to Wiktionary. :)