Help! beside an Ikea stool..? Hey, does anyone happen to have this stool? or a similar one..

Hey, does anyone happen to have this stool? or a similar one..

http://www.ikea.com/ca/en/catalog/produc...

I am having a really hard time getting the wheel to stay on properly.. they should just screw in but they aren't!
Answers:    My daughter have this chair in blue. My husband put it together within only a few mnutes. Works great. Re-read the directions, try again. I'd return it if you continue to enjoy problems.