Rear wheel on Huskee riding mower?

I have a very old Huskee riding mower. I had to remove the right rear wheel/tire to pump it up and when I placed it back on the rear axle, replaced the "C" clip, etc., it will no longer move (it was working fine before I took the wheel/tire off). The wheel I replaced just wobbles on the shaft. Keep in mind that I am a woman trying to do this on her own so I felt very good about at least getting the wheel off to put air in! Could it be that the "C" clip isn't in properly?