switching themes help

general:

http://codex.wordpress.org/Using_Themes

do you have the other theme installed?

I changed the image and enter the title of the page, put it doesn’t change.

? what are you referring to?

I am not sure what you are trying to achieve (?)

do you want to switch theme?

or do you want to change the header of your existing theme?

can you post a link to your site to illustrate the situation?

what theme are you using?

without knowing the name and download link of the new theme, and possibly a link to your site, it is virtually impossible to suggest anything to help you.