There are a few ways to change the serving/portion size:
1. When creating an automated meal plan you can choose the serving size and it will reflect that amount of servings for that entire meal plan. You'll see the prompt when you go to create the plan.
2. Under your preferences. This will then be your default for your plans going forward (You can always change it per plan if needed)
Your preferences are located in the menu in the top right corner when you click your initials. Be sure to save your changes at the bottom of the page.
Changing your preferences does not change any previously made plans, only new ones going forward.
3. Within the recipe. This allows you to adjust the serving size just for that specific recipe. Click the title or photo of the recipe you'd like to change. This will be the best option if you need to adjust serving sizes after a meal plan has been made.