How to set up visual voicemail on iphone 5s?

Need help setting up visual voicemail on my iphone 5s don't know if it matters but it's with T-mobile.

Visual Voicemail (VVM)

Change greeting
To change the Visual Voicemail greeting, follow these steps:

From the Home screen, tap Phone.
Tap Voicemail.
Tap Greeting.
Choose one of the following:
Default
Custom
If choosing custom, tap Record, record your greeting, then tap Stop.
Tap Save.

Change password
To change the Visual Voicemail password, follow these steps:

From the Home screen, tap Settings.
Tap Phone.
Tap Change Voicemail Password.
Enter a new voicemail password.
Tap Done.
Re-enter the new voicemail password.
Tap Done.

Listen to voicemail messages
To access Visual Voicemail and listen to new messages, follow these steps:

From the Home screen, tap Phone.
Tap Voicemail.
Tap on the message you wish to listen to.
The message will automatically start playing.

Set up Visual Voicemail (VVM)
To set up Visual Voicemail the first time, follow these steps:

From the Home screen, tap Phone.
Tap Voicemail.

Turn off
To turn off or disable Visual Voicemail, remove the visual voicemail feature from your account.

There are no settings to enable or disable Visual Voicemail on the device.