Here is my mini tutorial for ladder stitching something onto your softie. I am using Rudy as a demo but of course this is applicable for any attachments such as arms, saddles, etc.
Stuff your antler, ensuring that you turn in the raw ends before reaching the end of your stuffing. It is extremely important that you stuff both your Rudy and your Antler very firmly or you may end up with floppy antlers. Once you have turned in the ends (pictured) then firmly stuff the remaining section of the antler until you reach the opening.
Ladder stitch the horn into place as you ladder stitched closed the turning gap (from last tutorial). Take your next small stitch into the horn base (folded under edge) entering the horn at your point of exit from the head.
Unlike with ladder stitching the opening, I suggest that you pull your thread and stitches tight after every stitch along the way. Once you have gone completely around the horn I recommend going around a second time for strength. Once complete, tie a knot close to the base of your thread.
And then sink the knot into Rudy's head!
Once you have sewn the front edge to Rudy's ear, lay the ear down the opposite way and sew along the back edge of the ear so that the ear is securely attached and will stand up straight. Tie and sink a knot and - Ta-da!