Hi JJUK!
To fix your signature:
Click on User CP on the blue bar, top left of the screen
Click on Edit Signature on the left hand menu
To use your existing link, cut the link and re-paste it using the Insert Picture Icon (the yellow 'postcard' with mountains on icon thing!)
Click Preview Signature and confirm it looks right
Click Save Signature and exit screen
If this doesn't work - PM Beaver - he will know better!