I went into Tool, My OH, Profile, Message Boards...there are 2 boxes with your signature in it, the top one just shows you what your current signature is and the bottom one is where you edit it.
click on the bottom one so it highlights and then hit delete..then copy and paste the code from your new ticker into the bottom one and press save.
Sometimes it takes a bit to update. But if you sign out and then sign back in you should see it change.
Hope this helps! I just changed mine yesterday!