You can press on your profile icon in the bottom left corner to view your preferences page. It will look something like this:
Here, you can edit your username and photo, change the phone number and email associated with your account, and update your password.
We recommend that you link your email or phone number to your Sleeper account in case you lose or forget your login credentials. Otherwise, we will not have a way to help you recover your account.
You can also find some other settings in here for notifications, emails, and languages:
On the Web
You can find some similar settings on the web version as well. Press the settings icon in the lower-left corner of the screen, and use the menu on the right to move from account to profile or preferences.