This what I was advised by DavidS and it worked-First you need to go to your tank journal, and copy the address from the address bar of your web browser (highlight it all, right click and press copy)
If you go into your signature (click name on top right, go to signature) - highlight where you've got your tank name, and look up at the buttons above where the text is - one looks like a chain,. It should say something about edit/link or insert link if you put your mouse over the correct button.
Click it, and in the address box, right click your mouse and press paste. This should copy your tank journal address into it. Press any Save or OK buttons, and it should be done.