Why is my iPhone disable

This happens if you typed in incorrect passcode several times. The only way to remove this is to connect this phone to a last known PC that you've connected it to. After that open iTunes and it will ask you the password there. If you didn't connect it to a PC. Restoring the iPhone with iTunes will be your last option. Note that Restore will erase everything in your phone (unless you back up your phone via iCloud) and update your iOS to latest version.