There are several ways to share a comic on The Duck with others! Most of these options are integrated in the "share this comic" link in the topbar of a comic's page, which will differ based on whether you are logged in or not. However, the "share this comic" is available to everyone:
Clicking on "share this comic" brings up a popup with the option to add your own comment and forward on to several social networking services (which require their own log-ins):
The "share this comic" option only applies to specific comic pages (the one you are viewing when you click on the topbar link) and not the comic as a whole.
If you have an account on The Duck you've got an additional ability to share: you can create a list of Recommended Comics which will appear on your profile page. To Recommend a comic on your profile page, click on "recommend comic" in the topbar which appears on each comic if you are logged in:
A recommended comic will then appear on your public profile: