Please follow the below steps:
iOS: Settings -> Log in/ Register.
macOS: Click on the iFax icon at the top-left corner of the task-bar -> Preferences -> Account -> Login/Register
Android: Menu -> Login/SignUp
Windows: Settings -> IfaxID -> SignIn/SignUp
Web App: iFax Web -> Click on the profile icon -> Enter email address to Login/SignUp
Please note that if you are not logged in while making the purchase, your purchase is linked to the device used. You will then just need to Log in/Register to your account on the same device to assign your purchase to your account.