bad request

Hi I am a total novice and I started my site with the Preferential Lite theme. I now wish to upload the childtheme zip file but keep getting “bad request your browser sent a request that this server could not understand”. I have tried to upload in Firefox and Chrome. I have also cleared my dns. Anyone have any suggestions please, I would be very grateful.
seedofcalm.com Think I am using latest version of wordpress but not sure.