I see multiplayer is still in beta then...

[doghous3]

When you join a server you'll see a map. A few icons along the bottom.

You first have to choose a side via top left.

On the map, click one of the airfields until it's highlighted with a red circle.

This then should give you options on teh right to select squadron, plane, etc. Scroll down and you'll see create.

Hope that helps.