The ILL form used by this link is set up in Service Configuration. First, make sure that the resolver or form you want to use is set up in the OpenURL Resolver tab. Once it is added there, you will be able to select it under the WorldCat Discovery and WorldCat Local > Place Hold/Request Buttons > Resource Sharing (Any Level) > Type of Button Configuration setting.
Additional information
There is more on the Resource Sharing settings.