Learn Cisco Packet Tracer
wildcard /30    : /30 = 255.255.255.252
              : 255.255.255.255 - 255.255.255.252
                  : 0.0.0.3
wildcard /24    : /24 = 255.255.255.0
              : 255.255.255.255 - 255.255.255.0
                  : 0.0.0.255
(c)# router ospf 10
(c)# network <ip_address> <wild card> area 0
(c)# router ospf 10
(c)# network 10.10.10.0 0.0.0.255 area 0
(c)# network 20.20.20.0 0.0.0.255 area 0
(c)# network 1.1.1.0 0.0.0.3 area 0