In Pivot Stick Figure Animator, open the animation. Click save, and the save window should pop up. There should be a slot under the area where you type out the animation name. Click on the slot, and choose "GIF" or ".gif" file. Name your animation, then click save.
Go to
http://imageshack.us/ and click on the button that says, "Browse". A small window will open. In the window, look for the file you just saved. Click on file you saved, and click the "Open" button. Then on the ImageShack website, click "Host It!".
When it has loaded, you should see your animation. Copy the URL, and post it.