Here are a couple basic things that you should know when setting up a network. You may have allready completed steps 1 and 2, i only included them to give a broader outline on setting up a basic network.
1> Your computers need to be a member of the same workgroup, you can check this (in XP) by right clicking 'My Computer' select 'Properties' then select the 'Computer Name' tab. The workgroup name is displayed here, you may also change the workgroup name by clicking 'change'.
2> If you are not running a DHCP service then you will have to manualy set IP addresses for each computer (It is unlikely that you will have a DHCP service running unless you are connected to a router). To set the IP addresses open netowork connections and select your wirless adapter, right click and choose 'options'. Then if not already selected choose the 'General' tab, scroll down the list and double click 'Internet Protocol (TCP/IP)' from here you can setup you IP address and subnetmask. As a rule i would use:-
192.168.0.1 for the IP address of the first computer, then 192.168.0.2 for the second etc etc...
Use 255.255.255.0 for the Subnet mask on all machines.
3> Once you have a done this you should be able to see both computers in the 'My Network Places' window. Now all you need to do is tell windows which folders you wish to share, this is done by simply right clicking the folder you wish to share and clicking 'properties' and selecting the 'Sharing; Tab, then jsut click 'Share this folder' and either use the default name or choose you own. Once you have done the folder should be visible in the 'Network Places' window and allow you to share files betwean computers.
Thats the basics of it. Hope this helps?