Hi Harika,
You can change the default logo in the layout of the page.
First check which layout is applied to the page and go to that layout.
Like you can see in the below screenshot, the Layouts folder there with Atlas_Default and Atlas_TopBar
There you can find that logo image.
Change that logo image to your desired one's.
Hi Harika,
You can duplicate the layout you are using and simply replace the logo with your desired logo