How do I ship to Custom Object (or object other than Leads, Accounts, Contacts, Opportunities)?
Be sure the FedEx app has been installed for "All Users"
Please do this even if you do not wish to grant access to all users in your Salesforce org.
We will use the Case as our example, but this can be ANY object in Salesforce. After installation, you will need to add the FedEx Shipments related list to to the object page layout. If this is not available to you, contact your Salesforce Administrator: