When adding items into the meal plan, you can select the "add item to [meal]" and add foods from a list of your favorites, from a meal search or add individual items from the "advanced search."
To add a meal or an item, select the "add item to [meal]" and while in the "favorites" tab, scroll to the bottom. There will be a button to "build a new favorite meal." Select this, enter the nutritional information, and select "save." It will automatically be saved to your list of favorite meals.