In the User Administration area of the ISN you can add a signature for each user.
Click on Admin -- User Administration
Next, select Edit from the Actions Menu
Next, scroll down to add the signature to the user's account.
NOTE: Make sure this signature is closely cropped to the size of the signature itself and is not a huge image.
Upload the signature file from your computer by clicking on the Upload Signature button. Then scroll to the very bottom of the page and hit Save Changes.
From there you can use ANY of the replacement values for the signature in your templates or agreements: