When a client checks out a package, they will be prompted to input a password and create an account:
Moving forward, clients will have to login in order to access their package link (post purchase/checkout) on Practice. Their browser will likely save this so it won't be required every time.
Admins will also be prompted to login (with their admin credentials) when viewing a client's package instance:
Clicking "View as client" will prompt a login that your browser should cookie and save moving forward.