API Keys are an alternative to using a single WebAPI password. Each computer is allocated a unique ID, that can then be used to control access to other computers running different services, such as Indexing, or Crawling.
Services running on the same computer are pre-authorized, no further action is required.
To register a remote computer, copy the ‘Local PES Key’ from the remote computer, and paste it into the Registered Remote Keys of the local computer.