After logging into VRChat with your Steam, Oculus or Viveport account, open your quick start menu, then select Settings. Near the bottom of the menu, select the button to Upgrade Account and follow the prompts from there.
The token code will then be pasted into the VRChat account link page. This will merge the Tafi Avatar Creator to the VRChat when completed.
By closing and reloading the Tafi Avatar Creator application, a pop up box will appear to connect the accounts.