Go to control panel > sales > manage sale processes > either click on the current sales process that you see or create a new one.
You can either add a new sales process of edit an existing one. New sale processes can only be assigned to new sales, meaning you cannot change the process for sales that are active. This is why you might want to edit an existing sales process rather than creating a new one.
Editing an existing sales process:
Edit a step within the sales process by pressing the pencil symbol on the right.
Here you can change the name of the step for this sales process, the person it relates to (Vendor or Buyer) and lastly the order of the step.