How do allow someone to create Opportunities in my Organization?

read opp manager

As an Organization Manager you are able to grant Opportunity Manager permission to users. This permission level allows that user to create new Opportunities within your Organization and manage them. Once this permission level has been granted, the user will not automatically become an Opportunity Manager in any existing Opportunities, or Opportunities created by other users. If they need to have access to specific Opportunities that someone else created, they will need to be added and granted the Event Manger role manually. If the user needs to have access to all Opportunities, then full Organization Manager permissions may be the route to take.