There are a few things you need to do.
Flattening is a must - oval cross section like SFL said.
Next is to poke a hole about three rings down on the 'in-pole' end of the tube.
Pull some heavy guage wire or strong rope throught the pole from the top through the holes on the bottom.
Loop the wire through the holes in the tube so that you have two ends of the wire up through the top of the pole (this is done so you can release one end and pull it through the hole in the tube, out the top of the pole).
I've found that windex is just a slippery as wd-40, and a whole lot cleaner.
Push the tube while pulling on the wire through the hole.
The last time I had to do this, I got the tubes in within 5 minutes.
Hope that helps!
You'll LOVE that pole.