The BES Clients will report whether or not a BES Relay is installed and every time you send out an action as a master operator, the BES Console automatically updates the list of available relays.
So, there is nothing you need to do other than to wait for the BES Relays to report in and then send an action (any action) as a master operator.
Correct. Whenever the BES Relay is deleted (right-click on computer and delete), the BES Relay will be removed the next time the master operator sends any action.
For manual selection, the BES Clients/Relays don’t really need to know about each other. The BES Console knows about all the relays and it allows you to select which ones to use from the list of all relays.