ARToolKitPlus doesn't have support for camera/video input so you should used it in combination of another video library such as DSVL, videoInput]2 or camera input from OpenCV.
For ARToolkit, there is a discussion on the topic (standard camera parameters to artoolkit format) in the ARToolKit mailing list:
http://www.hitl.washington.edu/artoolkit/mail-archive/message-thread-00422-camera-calibration.html