Easy to remember as it is exactly the same as هِيَ.
Add تَــ at the front of the verb and the vowel of the last huruf of the verb is dhommah.
You sit - تَجْلِسُ
To differentiate between هِيَ and أَنْتَ, we need to know the context or depending on the sentence.
If the verb is referring to a girl, we know that it refers to هِيَ and it will be translated as She sits.
If it refers to a male, we know it is for أَنْتَ. It translates to You sit.