Stitch the pattern together, using a basting (long) stitch; don't bother pressing seams since you can't press fur anyways.

1) put good sides together of both front leg pieces, stitch crotch seam. Do the same for the back leg.

2) good sides together, pin inner leg seam, matching notches and seam. Stitch.

3) Still with good sides together, pin and stitch outer leg. Leave inside out.

Now is the fun part. Try them on with the padding (i just carved some foam, just a knee cap and a pit of padding to shape the calve. You don't need huge pads either, just enough to imply the shape honestly) pinned in place. Pin along the sides to get the fit you want, be sure to leave a bit of extra at the joints (not much though) for movement.

Restitch along pinned pine (and remove pins before you break a needle on them) and try on again. Leave the padding in, it's easier that fighting it. Trim any excess once you get it fitted just right.

As you can see, I've only fitted one leg for the sake of this picture. Note the shape and difference in size. I'd take a picture with it on but since it doesn't go up as high as I want.

Also, try them on with them different pairs of pants on (assuming you'll do pants with them on) to see if the fit will work with more clothes.

At this stage, trace on the patterns you want to do with fur (brown sharpie) and get ready for cutting the fur!