In PubMed your Link Resolver is configured using the LinkOut Library Submission Utility. Login with your institutional account and edit your Outside Tool Base URL there.
Remember to use the PubMed-Specific LibKey Link which has a syntax like this:
What if you don’t presently have a link resolver integration into PubMed… but would like to? LibKey Link requires that the library first establish an otool registration with PubMed. We have a guide here that discusses this process.