How do I get my Apple ID? The clerk set up my phone for me but she failed to give me my passcode.

Perhaps you ARE using a trusted device which is entering your credentials for you.

Look in Settings -> AppleID [Name] to read your AppleID. (The e-mail address in small print right under your name)

Then …

Change your AppleID password to something more memorable:

If you forgot your Apple ID password - Apple Support

You signed-in here w/ an AppleID and password ???