To log in, whether on the browser or the application, it will always be the same method: by indicating in the "E-mail or nickname" field the e-mail address or the nickname that you gave when you created your account or by clicking on the "Log in with Facebook" button if that is the option you chose.
We frequently receive reports of missing purchases or inactive subscriptions on an account. In most cases, people are simply not logged into their account.
If an account is already logged in on the device you are using, you can change it to your own by going to the "My Account" menu and choosing "Change Account".
Then enter your login and password, and that's it! You will find your account, your games, and your purchases.