Oliver, first I'd suggest you upgrade your code stream to something a little more current. There have been numerous enhancements since the 3.0 IAP code base not to mention bug fixes.
In the 3.4 code stream:
To configure Local, Local,L3, and Centralized,L2 DHCP scopes:
1. Click More>DHCP Server at the top right corner of the Instant Main window. The DHCP Server window is displayed.
2. To configure a Local, Local,L3, or Centralized,L2 DHCP scopes, click New under Other DHCP Scopes. The New DHCP Scope window is displayed. The following figure shows the contents of the New DHCP Scope window.
If you want to do this in the newly supported CLI in the IAP (3.4):
To configure Local DHCP scope:
(Instant Access Point)(config)# ip dhcp <profile-name>
(Instant Access Point)(DHCP Profile<profile-name>)# server-type <Local>
(Instant Access Point)(DHCP Profile<profile-name>)# server-vlan <vlan-ID>
(Instant Access Point)(DHCP Profile<profile-name>)# subnet <IP-address>
(Instant Access Point)(DHCP Profile<profile-name>)# subnet-mask <subnet-mask>
(Instant Access Point)(DHCP Profile<profile-name>)# dns-server <name>
(Instant Access Point)(DHCP Profile<profile-name>)# domain-name <domain-name>
(Instant Access Point)(DHCP Profile<profile-name>)# lease-time <minutes>
(Instant Access Point)(DHCP Profile<profile-name>)# option <type> <value>
(Instant Access Point)(DHCP Profile<profile-name>)# end
(Instant Access Point))# commit apply
When you then define your SSID paramentres, set the mode to NETWORK and select your prevsioulsy defined VLAN/DHCP scopes and you should be good to go.
Cheers, Adam