I just installed mine last night so I know EXACTLY what you are talking about.

I had to do it by myself which made it harder. It is easier to do when someone pushes the intake from above. Everytime I pushed the K&N filter on to the tube it would push back up through the compartment.

I went over to my bench press and pulled off 50 lbs of weight, threw a towel over the intake not to damage it, then put the weights on top of the intake to simulate someone pushing from above. I then walked over to the sink with my K&N and applied a little water from my finger to the inside of the rubber on the filter. I was able to get the filter on fairly easy.

The hose clamp was a different story. I tightened it from under the jacked up car but it poppped the filter off. I had to use one hand to hold the filter on and one hand to tighten the hose clamp.

 

When I used to heat I was able to get it on easily by myself. Maybe you didnt push it on enough if the clamp is making it pop off. I would keep an eye on it to be sure it doesnt come off like mine did. There should be a little hole you can peekin to make sure its still on.