It usually means 'relax' (in an enjoyable sense), or 'calm down' (if someone is angry/agitated). It can sometimes be a criticism of laziness, e.g 'He likes to take it easy' (He doesn't do much work, he is a bit slack or lazy)

It does depend on context. Perhaps 'they' are relatives, or people at a spa or drug/alcohol rehabilitation centre. Whoever they are, they will make me relax or destress.

The context here is not enough for me to understand very well. However, the following example might be helpful. Imagine your friend is driving a car and you are with your friend. Now, imagine another driver turns quickly in front of your friend. If your friend becomes angry and decides to start yelling at the other person, you might say, “Hey, take it easy,” to your friend. In this scenario it is like telling them to relax. I hope this helps. If you don’t think this is the correct sentiment, try providing some more of the dialogue from the move.