Child Limbs

Lets look at the proportions for the limbs before we go on.
LEGS- to get a simple measurement and location for the knee, use the head height from the crotch to the knee (number 4 on the drawing). Keep in mind that the upper leg extends past the crotch to the hip joint or a measurement of 1-1/4 heads in this case. The lower part of the leg is the same length of 1-1/4 heads to the ankle joint. The ankle to bottom of the foot is going to vary but should be about 1/8th of a head high.
ARMS- For most figures, the following rules apply: the shoulder joint is located at the end of the collarbone. This is the start of the upper arm. The shoulder muscle (deltoids) will make the shoulder slightly higher than the joint.
The elbow hits the space between the ribcage and the hipbone (pelvis) on the side of the body. On the drawing this is shown by the two faint lines on the side; the downward arching one is the bottom of the ribcage, the upward arc is the top of the pelvis. Use that same measurement from the shoulder joint to the elbow as the measurement from the elbow to the wrist.
!!!!NOW, take all the proportions and rules I have laid out and disregard them!!!!
Every person I have met has a slight variation to the length of the toros, legs, and arms. You must adjust the "rules" to create a body which pleases you. BE AN ARTIST! Experiment with the form and make art which is beautiful to you. I give you permission to ignore all the rules for the sake of your artwork!

Having said that, lets take a quick look at how to manipulate the clay into some kind of humanoid limbs.

 Condition your clay and press it onto the armature. Add a little more clay than you need.

 This is not the pretty stage, just get the warm clay on the wire without air bubbles under it.
Use a very sharp knife to cut the profiles of the limbs. A dull knife will rip the clay and leave white marks in your finished surface.

Let the clay cool before you do your final shaping and smoothing or you will be pushing hot clay off the armature as you attempt to finish the sculpture. Work back and forth from limb to limb to let the clay cool as you finish them.

 Have a great day!
Mark