From MikroTik Wiki
/ip firewall address-list
Firewall address lists allow user to create lists of IP addresses grouped together. Firewall filter, mangle and NAT facilities can use address lists to match packets against them.
|address (IP address/netmask | IP-IP; Default: )||IP address or range to add to address list|
|list (string; Default: )||Name of the address list where to add IP address|