Author name display change

I would like to change the way display author's name. When I got text and pictures from other blog, I wish it would be displayed "by (author) via (website)' so the credit could go to the original author. Could you help me? I used 'Simple Catch' theme on www.gorket.com. Current: By (Log-in person id) I want : By (author name) via (website name) Many thank you in advance.