Look at your attachment.
what you want to do is code modification other than changing the name of your site Coinwash.com
This falls outside product support since we support the code as it is written. I could refer you to post in our modification forums if you choose to post there where support does not respond.
If you make edit noted in this thread that will remove the powered by which is what you asked.
If your looking at something else your looking at editing even more code files since the title is also added to depending on the script
See this example here in showproduct.php
Code:
Content visible to verified customers only.
If you want to print nothing but site name you could change it to this
Code:
Content visible to verified customers only.
Now any other discussion on this you can post in the modifications forum since this is not a support request.