You need to have Assign Agent Rules add-on installed in order to assign agents automatically depending on conditions set. Automatic assignment of ticket is not possible in free version.
How can I add an agent?
You can add an agent in Support Agents submenu.
What is an Agent?
Agent is user who reply tickets on behalf of the website owner.
What is Agent View and Customer View?
Agent view is ticket list visible to agents whereas customer view is ticket list visible to customers (users other than agents).