The command is snmp-server community YourString RO (or RW if you want read/write).
I would recommend not using any default community string on your devices. I believe in SolarWinds you program a community string when you add the network device to it so you can pick what string you want to use.
community strings are version 2 which are clear text. Version 3 offers encryption. To enable traps on your cisco devices use snmp-server enable trap (doing so will enable all traps on your device)
snmp-server community <community_name>
snmp-server ifindex persist
snmp-server trap-source <loopback>
snmp-server host <host_ip> version 2c <Community_Name>