You want to add this code into article view or in general inside template?
For standard articles: templates\gk_creativity\html\com_content\article\default.php
For K2 items: templates\gk_creativity\html\com_k2\templates\default\item.php
But
I am trying to figured out how to include <jdoc:include type="head" /> line using the documentation
What is funny inside templates\gk_creativity\layouts\default.php, line 51
there is <jdoc:include type="head" /> - so I don't know what they want from you !?About RSSeo! - sorry, but we can not support all commercial extensions . I even can't check without buying it, so next time read documentation from component before not after buying.