Go to your trip report and copy the link from the address bar. Then go in to change your signature and position your cursor where you want it. Click on the add URL icon which looks like a paper clip with a globe/blue ball and a box will pop up. Paste the URL you copied into that box (make sure you get rid of the extra http// that is automatically put up in the box.)
Preview your Signature to make sure that you like it as it is and if not then you can adjust it. Otherwise Save the Changes.