The UPS API uses OAuth to allow the app to fetch rates from UPS on your behalf.
In the app, clicking the button to "Authorize UPS API" will take you to a page for you to log into your UPS account with your normal UPS.com username and password. Once authorized, you'll be taken back to the app and can then enter your UPS account number and save the authorized credentials.
Log in to your FedEx account and follow the FedEx Web Services guide to get your production keys.
Record your Authentication Key, Account Number, and Production Meter Number at the end of your registration process because you need it to activate FedEx in the Shopify admin.
Your Meter Number is emailed to you by FedEx, but the authentication key isn't. Make sure that you record the authentication key before proceeding.
Check for an email from FedEx that includes your Production Password, Account Number, and Production Meter Number.
Login to Canada Post website
Click the green 'Join Now' button, and follow the steps to create a developer profile, the production key information will be waiting at the end.
Contact your DHL rep for getting your credentials.