If you want to add your Social Networks related to your Company on your Company Profile, you have to login with your username and password.
Once logged in, mouseover on your Username, and select "Edit my business" on the dropdown menu.
Just on the Contact Details in your Control Panel, you will see the option to add your Social Networks. You can add either your Facebook, Google+, Twitter and LinkedIn profiles.
Once you are finished, click on the "Save Changes" button.
When your potential clients enter your Company Profile, they will see your profiles below the "About Us" section.