Desktop
Click on the recipe you would like to move and drag it to the day and meal where you would like it. You will see a light gray box show up to indicate it has moved. Make sure to drag the recipe/item to where the recipes are located, above the servings and nutritional info.
Mobile
At the top of the screen, you will find the days of the week. Simply click on the day you would like to see.
Note: It can be harder to navigate the entire meal plan on mobile, so many people like to look at the weekly view on a computer or tablet when manipulating their meal plan at the start of the week.