K2 for cb is a plugin for Community builder really easy to use.
Once installed in the panel of community builder can edit the graphics settings for cb and k2 indicate the id of the category of k2 which will be included in the articles.
For the category of k2 is advisable to create a new one, where we give permissions to users to create and edit their own articles. In this way the frontend, the profile of community builder you will see a tab "k2 cb" where the user can create the most complete articles editor to insert images and custom form.
The particularity of k2 set of custom fom extends much thanks to this plugin the potential for Community builder.
For any doubt or question please feel free to contact me!

Requirements:

file_get_contents enabled in the server configuration