When you stitch two fabric pieces together, you must leaving a small opening to reverse right side out and stuff.  After you reverse and stuff your toy, you will need to stitch the opening closed.  You can do this with a ladder stitch.  

How to Ladder Stitch:

Step 1. Fold seam allowances to inside and if desired, press flat with an iron.  The fabric will be easier to stitch if it's flat.

Step 2. Thread needle with sturdy thread. Make knot at end.

Step 3. Hide the knot at the end of the thread in the seam allowance. Bring needle up at beginning of opening.  Note, I am using black thread so that it’s easier to see in the picture.  You will want to use the color of your fabric.

Step 4. Insert needle in opposite folded edge directly across from position where needle came out of first folded edge. Take a small stitch; pull needle through fabric.

Step 5. Return needle to first folded edge, starting that stitch directly opposite of where you ended the last stitch and take another small stitch and pull needle through fabric.

6. Continue in this manner to make a few stitches from side edge to side edge until you get to the end of the opening.

7. Pull thread snugly to close opening.

8. Secure thread end with a backstitch or two, cut thread and tie to secure.

9. Trim any excess thread