I have found ,in the theme section " logo.zip ", where i have to install logo
usually in ur theme's images folder, u will find that theme's logo
just replace it with urs
If you have found a zip folder on a themes download page called logo.zip you don't upload it anywhere.
That folder contains the files to edit the themes logo - if you want to edit the themes logo you would unzip the folder, edit the image, then upload that to the themes image folder on your site.