1. Click on the 'Airport' icon. Choose 'Create Network'.
2. You can change the name or leave it as the default. You can also keep the same channel or choose a new one. If you want it to be secure, use a password, and this will make WEP required. Unfortunately it is just WEP, but it's probably fine for temporary use.
3. Now your airport should list your new network and connect you to it.
1. Go to the 'Airport' and select the network you created on Mac #1.
2. Enter a password if you need to.
3. Click on the 'Finder' to make it active.
4. Finder -> Go -> Network. Click on the 'Network' link.
5. You should see the other Mac listed if sharing is setup properly. 'System Prefs -> Sharing'.
6. Double click on the Mac name and you should get the option to 'Connect' or 'Share Screen'.
7. When you are done with your network, go the airport menu and choose 'Disconnect'.