Hi renada,
[ol]
[li]Go to your templates in Joomla backend[/li]
[li]Make a copy of the Cashmere template[/li]
[li]Set it as default[/li]
[li]Enter the Cashmere template settings[/li]
[li]Open Logo in the menu[/li]
[/ol]
There you wil have a small manual how to change the logo.
Basicly you can stick to the steps in the Tutorials-Template Customization-
Adding a different logo for each langauge on joomla51.com
Just skip the steps for the languages.
Regards, Marek