How do I get my picture the right size for a background on YouTube?

I like some of the pictures I take, but YouTube keeps telling me it's the wrong size to upload as a background. How do I change the size to the right one?How do I get my picture the right size for a background on YouTube?
You can use almost any type of image editing software, such as paint. In paint, there is an option to resize an image to a certai number of pixels.How do I get my picture the right size for a background on YouTube?
You have asked a good question, I wish you would have also mentioned if you are using new youtube beta or old one. Anyway you can try the following for one background image. Please remember it is advised you set Transparency as you like when you change background image. Unless you click save changes button nothing will be changed so you can test by choosing various setting and when you are satisfied click save changes.

1400x1200

1200x2000

This is my profile page for example of new beta background. Size I used here is 1800x3500

http://www.youtube.com/user/nihon94b



How to use your photo as a background. First open any photo editor import the image you want to use as a background. Then change the size as I have mentioned. When saving keep your image under 256 KB. If you need any help please send mail to nihon94@yahoo.com