To join a deposition, first go to login.agilelaw.com and click Join Deposition below the "Sign in to your account" header.
This brings you to the Join Deposition screen. Input the PIN number for the deposition along with your email and name. Then click Join.
If the PIN number is correct, you will see this screen.
The person conducting the deposition must admit you into the deposition before you are allowed in. Once you are admitted, you will see a screen like this one.
Next: View the Witness Screen.