Click on your user name Top Row to the right of the date on the main page.
Select Signature
In the box that looks like a message box enter your signature - Or past a the URL to your journal.
You can also type something like ----- My First Journal then highlight "My First Journal" and select the link icon (looks like a chain to the left of the Smiley Face) and link you URL to the highlighted words.
Hope this helps.