Hello. Iam new to K2 and i dont know much of it.Can you tell me where can i get tutorials for user profiles and user blogs?If i want to create community with K2 i should sign up at ning network?

For info on JoomSocial integration please see
community.getk2.org/forum/topics/k2-and-jomsocial-full?commentId=3536014%3AComment%3A12220 (older thread) and
community.getk2.org/forum/topics/k2-jomsocial-full-integration?xg_source=activity (more recent)
There are commercial components/plugins at extensions.joomla.org/search?q=k2
which may be helpfull also