If you have just downloaded AnkiApp for the first time, you will need to "Sign Up" for a new account before you can "Sign In" (see bottom of page for Sign Up directions).
If you are logging in to AnkiApp from another device and previously have signed up, choose the "Log In" option—there is no need to create a new account.
Note: AnkiApp uses different credentials than other "Anki" services (including AnkiWeb)—see Is AnkiApp the same as Anki? for more information.
If you have other problems with login, please contact support via the in-app "Help" page, or email email@example.com and describe what issue you are having and/or any error messages you receive.
How to Sign Up for an AnkiApp Account
Open AnkiApp, then follow the directions in the images below.