When you are viewing a recipe, click on the link "Add to meal planner".
Then choose when you want to eat that meal (date , Breakfast / Lunch / Snacks / Dinner ) and click OK.
If you want to add a recipe in the meal planner, another option is to open your meal planner and tap on the + button
Then click on the desired recipe, select the day and the time, and click on Add
If you want to change the date of a meal, tap on the edit button at the top, then select the recipe in the calendar and drag it to another day.
If you want to put your recipe in the dinner section, select the day, then click on edit button on the right of your recipe. Select dinner in the popup.