We are really in Alpha and hope to actually release an installable Beta within a couple of weeks.  Documentation is certainly not complete at this point although I can help you along.  I am planning a series of screencasts to help with the documentation problem so stay tuned.

As for your questions... Liferay has been removed in Kablink 2.0 so there are no portlets you need to add.  If you are logged in as Administrator you will have an option under the "Manage" menu called "Site Administration".  This will give you full access to all the options we had in the Administration Portlet.

Adding users can be accomplished by navigating to the top level of the "Personal Workspace" area.  There you will find a list of users on the system and the option to "Add User" at the top.  This will work.  The Site Admin function to Add User should also work but you have apparently found a bug :-).  I will look into this.  Thanks for the find.