You can either choose to add your entire week or each individual day to your diary.
Add week to diary
Select > Food > Menu Plan > + Add to Diary (this can be found in the upper left corner) > Un-select what you don't want to add, and just check the calendar that you are adding it to the right day/week > Submit > Add to Diary > Go to Diary.
Add day to diary
Select > Food > Menu Plan > Click on the day that you're after > + Add to Diary (this can be found in the upper left corner) > Again check the calendar to ensure it is being added to the correct day > Submit > Add to Diary > Go to Diary
Be sure to click each step just once, you may have to wait a few moments until it takes you to the next step, but follow it through to your diary to confirm you have added it just once. This will prevent you from adding multiple copies of your menu plan.
If you are taking the more flexible approach, and not following the menu plan you can simply add foods and exercise directly in to the diary. Do this by clicking on Tracker > Food & Exercise Diary > Typing in the Add a Food or Exercise bar in the Morning, Afternoon or Evening section.