The "Application URL" field is not available in Partnership Federation. It is only available in Legacy Federation.
Policy Server: All current versions (up to R12.52 SP1 CR5)
1. Create a partnership with all the required fields except for the Application URL. Activate the partnership. The partnership needs to be in an "Active" state, otherwise you will not be able to see the "SAMLv2SP" object through XPSExplorer as mentioned below.
2. Now run XPSExplorer using the command line and follow the steps:
a. Enter "145" or the number that corresponds to the "SAMLv2SP" object
b. Enter "S" to search for objects
c. Enter the number corresponding to the Partnership you want to modify
d. Enter "W" to get a writable copy of the Partnership configuration
e. Enter "06" to modify the ApplicationURL
f. Enter the Application URL you want to use in the "New Value" field
g. Enter "U" to update the record
h. Enter "V" to validate the record
i. Enter "Q" four times to exit out of XPSExplorer
3. After you add the Application URL to the SAMLv2SP partnership object as above, you still won't be able to see it in the Partnership as a field. It would only be seen in XPSExplorer.
4. It is very important to note that each time you deactivate the partnership and activate it back, the Application URL needs to be added back in through XPSExplorer.
A product defect is currently open with CA Engineering to address this issue in the coming releases.