How do you set the configuration bits for a PIC 16F1829 in MPLAB X?
In MPLABX there is another great option, there is an interactive code generation tool which produces code to copy and paste in. This tool can be accessed through the menu bar: Window/PIC memory views/configuration bits.
from there it looks similar to below.      

Address|Name    __ _   |Value|      Field |Option     |     Category__ _ _ _ __|  Setting
       _
300001  _|CONFIG1H _| 07 _ _ |OSC_ |RCIO6_ |Oscillator Selection bits|External RC oscillator

simply select your options from the option drop down boxes and view the changes on the settings column.
When all are set click "Generate Source Code To Output" then copy and paste 

justing's method is better for learning the part, this method allows new users to get up and running more quickly. Take your pick.