1. Open up C:\Program Files(x86)\Shibboleth\IdP\jetty-base\start.d\idp.ini and on the line jetty.sslContext.keyStorePath= change idp-userfacing.p12 to idp.example.ac.uk.pfx
2. You can now (re)start the Shibboleth IdP. In the command prompt type:

 net stop shibd_idp
 net start shibd_idp

(Or use services MMC snapin)

Check: On a different computer, visit your IdP status page at https://idp.example.ac.uk/idp/status in a Browser. the status page should be displayed without any certificate errors. Check the certificate seen by the browser matches that created above (and importantly all the intermediate certificates are in place) (If you are testing without the relevant external DNS records and firewalls in place you might wish to temporarily add an entry to your system hosts file C:\Windows\System32\drivers\etc\hosts so that you can test)

 <IP of IdP server> idp.example.ac.uk