If you wish to first make all of your participant assignments and not send any emails until you are done, please follow these steps:
1. Complete your initil setup of the SignUp without making any assignments.
2. Go to Manage in My SignUps (from Dashboard or Organize).
3. Make sure you have set your Email Preferences to NOT send notices to participants when changes are made.
4. Make all your manual assignments.
5. If you wish to notify participants after, use Messages to send them a message and tell them to click the link in the message to view their assignments.