To 'Select an Army' you click on one of the Flags near the top, either the Union Jack or the split German/Italian flag. Then you should see some of the airfields in White where you can go to select an aircraft.
HOWEVER, if you want the community to join your server or you want to join another server you should know the following:-
1C Maddox Games no longer exist and have abandoned CoD. You may find others playing 'out of the box' online but you may not. There were many problems with it. But all is not lost.....
The community have taken up the challenge rather than ditch the original version and they have made a couple of patches to sort out the many game problems. Most players use their patches. Their forum is at:
http://theairtacticalassaultgroup.com/forum/forum.php
You may want to go there, get their patches and join the fun.
Here's the patching FAQ's/guide:
http://theairtacticalassaultgroup.co...ead.php?t=6431
Best of luck
klem