Brussels to Arlon --catching the train?

Travel Info
Is there there a train stop at the Bruxelles Midi airport? If no, how can you get to it..via tram...bus, foot etc.??

I need to go from the airport to Arlon via train....was a little confused on the website, it sounded like there was a train already at the airport, any input would be greatly appreciated =)

Travel Tips

In Brussels (Zaventem National-I assume) airport go down to lowest level and take train to Brussels. Alight at Brussels Nord (Noord) and look for trains to Arlon and or Luxembourg/Luxemburg on yellow Depart/Vertrek posters go to the track (voie/ spoor) indicated on departure poster via underpass.
Train to Arlon/Luxembourg stops at Bruxelles Quartier Leopold, Charleroi, Namur, Arlon, Luxembourg. Have a nice trip
Others

There is a train stop at Brussels international airport yes but it is not Brussels midi. Brussels main train line has 3 city stops. Brussels north, Brussels central and Brussels midi. Eurostar comes/goes from midi. Trains from the airport run about every 15 minutes and most go into the city although a few head out of town. Those that head into the city may or may not stop before the Brussels main stations but within about 20 to 30 minutes they reach Brussels north, then central then midi. A one way ticket was 2.80 euros to any of the city stations from the airport. The conductors/ticket inspectors on the "airport express" are very helpful to advise which station you need to change for Arlon.

I have assumed you do mean Brussels international airport as there is also a Brussels charleroi used by Ryanair which is way out of town.

Later edit : but you live in Belgium so I would have thought you know all this anyway. Enjoy the trip.
Albert gave you the right answer!
enjoy Arlon!