Register and Checkout explanation needed

[jtbworld]

I can't find Register and Checkout on the Checkout Cart documented. When I test to use it it doesn't seem to do anything. Current site: https://jtbworld.com/all-apps-store
What is the purpose of register? I don't see where it asks for username and password to be saved.

[iWim]

Did you enable Allow User Registration in Joomla?
Go to Users > Manage > Options
It's the first option under the first tab...

[jtbworld]

Thanks, that helped.