This Is how you put a blog banner on:
1) If someone has made you a banner then go to where the banner is.
2) click on the banner,if u can or able to.
3)click prt sc sys rq on yor keyboard at the top.
4)go on paint or ms paint.
6)Cut out the bit you dont want by dragging it to the size then right clicking and going on cut
7)save it and give it a file name
8) log on to your blog and go on Layout
9)The top of layout should say navar bar underneath it should have yo
ur blog description or another banner which you had before.Click on Edit.
10)Click on something like : Upload image,and then find the image.
11)yoy should see your banner and under your banner should say placement under placement click instead or title and description.
12)click save and close it and click save arangemnet. and then view ur blog.
Sorry if this doesnt work,well its should do.I'm not quite sure how to explain how to do it cuz i usally make my own banners.Btw if u think its a lot of steps.Well..?? its not really cuz i just cut it down for u in smalll steps so it wont confuse u.And the only reason why i did this is because people keep asking me how to put on a bannner.Well this should answer your question.