Firewall Cisco Pix 515 Question.

Hi all, i need your help guys, i have a cisco pix 515 and i don't know who
to add a new subnet.

Well, my actual subnet (248) is full and i added another (248 too). After
some configurations i got see a new ip from the lan, but not from the
outside/internet.

Actual Subnet: gateway 192.168.1.1 ---> ips from 192.168.1.2 to 192.168.1.6

The new subnet: gateway 192.168.5.15 ---->ips from 192.168.5.16 to
192.168.5.20

What i haven't done? Please help me.