@Jancol - Just so I understand, you want the "Cher's Spreadsheet" to be a clickable blue link in your signature line, pointing to the spreadsheet URL that is currently spelled out at the very start of the signature line (the https://docs.google.....yadda yadda)?
First, go to the top of the page. Look right above the search box. You'll see your username next to the Inbox and Alerts.
Click that to drop the menu down. Then click the Signature link. That opens the box to edit your signature line.
Replace the words "Cher's Spreadsheet" with the following snippet of code. Just copy it from here and paste it into the signature box where you want it.