Before users can use a SSH key to log in to a system, you must associate that key to an account. SSH keys can only be associated with accounts for Unix systems, Generic SSH systems, or network devices. Although it is an uncommon use case, you can associate multiple accounts to one key. You use the System tab to associate keys to an account. See Adding accounts for a system for instructions on associating a SSH key to an account.
After you associate a key to an account, that account is populated on the Account Usage page (Infrastructure > SSH Keys > select a specific key > Usage) and on the Accounts page. See Selecting actions for an account for the actions that you can perform on the account.