1) Disable DHCP on the WAP, let ICS on the dialup machine hand out IP addresses. yo will have to change the WAP IP address to be compatible with ICS addressing, 192.168.0.x with subnet mask of 255.255.255.0.
2) Set ICS on the dialup machine (right click network connection, sharing tab>share this conection)
3) install wifi nic drivers in all machines (set for infrastructer mode)
4) configure passwords and wep/WPA (recommend WPA if available)
5) turn on all pc's, and you are done. internet will now work on all of them.