NOTE: I haven't tried this yet, but common sense tells me that you need to sign up separately and independently. This would mean, sign up for one, log out first, then sign up.
Another way of doing it, if the app indicates that the email you use has already been used is, just make up ANY doggone email; it doesn't matter, these apps never send out a confirmation email.
FE Access-- https://app.cartoonmaker.live/login/register