If it's just you and a mate, use Skype for comms.
For a one on one, fly on the ATAG server, pick the most northerly airbase in England, or the most Southerly base in France and both fly the same aeroplane. Arrange to meet somewhere, then go and shoot at eachother.
If you want to fly against eachother on opposing forces, i.e. one Spitfire v one 109, you would need to set up your own local server, unless you are prepared to fly a very long way before encountering eachother, whilst avoiding all of the nasties in the English Channel.
The ATAG server is there. It's up to you how you use it.
Have fun.
