My friend gave me his old iPhone and reset everything so I could use it. I set up an iCloud account, but when I try to sign in, it says that my username (which is my email) is invalid. How is that possible when I can use the same email to sign into my iCloud account online? What should I do?
Check your network settings, also go to iforgot.apple.com and enter your first and last name as well as the Apple ID email address to make sure that the account exists. If it does not identify it then it may be that you didn't verify your email address. If it does identify it then you may need to try restarting the device and the network connections to see if you are able to sign in (also sign in to the Apple ID page to verify that you can sign in after you have identified it as an Apple ID).