After your clients have scheduled your meal plan, they can manage their grocery lists. For the client perspective, see here.
The instructions below are from the Professional's perspective.
In the Meal Plan edit page, click the 'Preview' icon (1) on the right hand side. This will show you the client's perspective of your meal plan before they schedule it.
Click the 'Schedule' button (2).
Choose when you want the meal plan scheduled (3).
Scale the meal plan servings by choosing how many people it will be feeding (4).
Once scheduled, scroll down and click 'Grocery List' (5) to manage the list.
Click 'What I Already Have' (6) to hide those items.
Check off (7) the ingredients you don't need to purchase, and click 'Hide What I Already Have' (8)