To have your servers automatically be added to a collection use the contact string or location strings under snmp on the monitored servers and have your collections criteria in SIM sort on that. I monitor many state agencies/domains and to keep track of the the servers that belong to an individual agency my contact string is 001- Gran-ADS-FP
001 is the agency number, Gran is the domain, ADS is the group responsible for the servers, FP is the role of the server.
I've attached some screen shots of my SIM comsole.