Talk
Talking makes it so easier for a person to open up, to speak what they feel. It makes people light heartened, feels as if a burden has been put off. Making plans of going out, smelling the fresh air and letting ourselves in the nature.
The person might not feel like going out or talking for many days, weeks or even months. Just don't give up yet. Give them time, give them that soothing words of assurance that you wont leave their side no matter what. That's what they wanna hear.
KEEP IT SIMPLE.