"Your Conection to this site is not fully secure"

Help, Hi guys,

I´m having issues with the ssl certificate. In essense, the message on the Opera Browser is saying: “Your Conection to this site is not fully secure” when on the admin panel. When clicking on the ssl certificate icon, I get the following:

Your connection to this site is not fully secure. Attakers might be able to see the images you´re looking at on this site adn trick you by modifying them. Bellow it reads: Certificate (Valid). Along with information on cookies being used. How can I get this to give me the soothing little green lock that says secure conection? Please help.

What shoudl I do, a link to resolution would be great and time saving. I´ve just failed to find a solution online.