To edit an existing disclaimer login to the MSPControl and click on Disclaimers or go to Organizations > Exchange > Disclaimers.
Select a disclaimer you need to change in a list of existing disclaimers.
Here you can change disclaimer name and text.
Next, if you're done with this particular disclaimer, click Save Changes and Exit. This will save your disclaimer and redirect you to the list of all existing disclaimers. Save Changes button also saves your disclaimer, but leaves you on the same page where you can edit your disclaimer further.
If you need to delete a disclaimer, go to the list of all disclaimers and click the Basket icon in the right.