引用自 Bernardo：

How do I connect my phone number to my steam account?

How do I add a phone number to my Steam account?

To add a phone number to your account or manage a previously added phone number:

• Log in to Steam (using the application or a web browser) and click on your profile name located in the top right corner.
  
• Select 'Account Details' from the dropdown menu.
  
• Under 'Contact Info', select 'Add a phone number'. If a phone number has already been added to the account, you will see 'Manage your phone number' instead.
  
• Enter your phone number and select 'Next'. We will send an SMS message containing your confirmation code - Enter this code to verify that we have the correct information.
  
• You're done!

You will now be able to reset your password or transfer your Steam Guard Mobile Authenticator from one phone to another via SMS.

Please note that only one phone number can be associated with a Steam account at a time.

What features are unavailable?

Limited user accounts are prevented from accessing several features on Steam, including but not limited to:

• Adding a phone number from some countries or under certain circumstances