From LightWiki

This tutorial will run you through the basics of pinning in IKB using

First start by creating a pair of legs. Make a Null, and in the front view, use Draw Child bone to draw down from the null a Waist bone, then out for a Hip bone, then down for a Thigh Bone, and down again to make a Calf bone, and down to make a Foot bone, then forward to make a Heel bone. Select the Null and press ctrl-j to activate the Joint tool. If the root item is selected, you can modify any joint with this tool. In the side view, pull the knee forward a little, then press 't' to end joint editing. Rename the bones.

Select the Hip bone and use the Mirror Hierarchy tool to mirror it and get the other leg. Press ctrl-b to activate the IKBoost tool and right-click on the null and select Apply IK Booster. Select the right thigh, and by right-clicking on the blue number next to the red circle, Lock the channel (the Bank channel). Right-click on the circle and select [IK Stop] for the hip. If you drag an item below it in the hierarchy, it'll stop you affecting the waist or null.