To use the one click Google/Facebook log in, you will first need to link your Google/Facebook account to your edX account in your Account settings. To access these click the dropdown arrow in the upper right next to your username when you are signed in.
Click the Linked Accounts tab near the top, then you will see the buttons to link your social media accounts for one click sign in.
If you are signed in to your Facebook or Google account in the same browser, clicking the button will link this account. Otherwise you will be asked to sign in.
*Currently Microsoft account linking is only available to certain corporate Microsoft 365 accounts.