What you have to do is a bit of HTML coding. When you go to edit your signature, and you click on the LINK ICON, and then paste your URL into the box, the following bit of code appears: <a href or something "url something dot com"> url something.com <end url>
This site doesn't use < it uses [ but whatever. Now, see that there are three parts to the code: the beginning < a href something "url something>
the middle probably highlighted in blue: url something.com
and the end bit: </a> whatever.
The middle part is where you type anything you want to appear as a live link. It is all highlighted and ready for you to substitute your preferred text. So you write
my 1st grow
and it shows up as a live link
Hope this helps