Error uploading photos

I updated to the newest version today and now I can’t upload any photos. I have resized them to the appropriate size. I have never had a problem before and now I can’t do anything. My blog has basically become useless and slideshows I promised to post to clients today are not a possibility right now. Can someone explain to me in simple terms what I need to do. I don’t understand all the talk about permissions 755 versus 777. I need help to be able to post my slideshows again!! I wish I could talk to a person but it seems this is the best way to get assistance and I really need it. Thank you so much!!!! 🙂