If MapQuest on your iOS device isn't locating you properly, a good first step is to ensure that Location Services are enabled on your device and that MapQuest has permission to use them.
To do this, simply open your iOS Settings app and choose “Privacy,” then “Location Services.” From here, you'll be able to ensure that Location Services is toggled to ON for both your device and for the web browser app you use (scroll down for individual app permissions).
To learn more about iOS location settings, including instructions for older versions of iOS, please feel free to read through this help article: https://support.apple.com/en-us/HT201357