Here are the suggested words to fill in the blanks:

1. **vital**
2. **support**
3. **free**
4. **together**
5. **difficult**
6. **stressed**

So the completed passage would read:

Friendship is a **vital** part of a teenager's life. Friends provide **support** and companionship during a time of many changes. Many teenagers enjoy spending time with friends at school and in their **free** time. They might hang out at the park, play video games, or go to the movies **together**. Good friends help each other through **difficult** situations. When a teenager is feeling down or **stressed**, a supportive friend can make a big difference.