AI use the winbecklers buttercream recipe, apply a thin coat to my cake and then chill to get it hard. Then I apply my fondant but it will not get smooth it has these bumps in it. Can someone please help.

You might be rolling your fondant to thin. I use to do that to try and save on fondant but realized that it was better to have it a bit thicker and smooth then to roll it to thin and have problems with bumps and tearing. Also, make sure your buttercream isn't too hard so that it any bumps will smooth out as you smooth your fondant.

Hope that helps, good luck.