Cisco IOS 12.0 dot1q problems!?

im working on an old router for my CCNA3 Skills based essment but the test was written for a newer ios version. like it says, im using IOS 12.0. i type in "encapsulation dot1q 1" for my vlan but the router doesnt support the "encapsulation" command. i tried to enter an ip address on the subinterface but it says i need to activate dot1q first... help???