Your time capsule has a default password when you first get it, "public". I highly encourage you to change it to something else. Since everyone knows the password, you want to change that right away.

Here's how:

Type in Airport so that you can see the Airport Utility come up

Then click Return to open it up.

Click on Manual Setup

1) Enter your Password

2) Click on ok

Click on Time Capsule to be taken to the area to change your password.

3) Change your password if you need to

4) Click Update to save changes.