1. Download the file from Citrix
  2. Unpack the zip and copy the files to the root home dir on your machine
  3. SSH in and type
    xe patch-upload file-name=XS62ESP1.xsupdate
  4. Wait a few mins and it’ll spit out a UUID when it’s done. Use this for the next command.
    xe patch-apply uuid=0850b186-4d47-11e3-a720-001b2151a503 host-uuid=5b280513-bfcf-4ce0-9d49-25aa61c110d9

The host-UUID which helpfully tab-completed on my system. You can also find this in the XenCenter management UI.