By default, the weekly meal planner will automatically run once a week, and send you your meal plans by email the day before your chosen grocery shopping day. You can't change the interval that the automatic planner runs on, but you can still generate plans for 1-2 weeks and then modify your grocery list to be for any days that you want.
So first, generate your meal plans (if you'd like to generate different weeks, you can change your grocery shopping day to achieve what you want. Instructions on changing your grocery shopping day are at the bottom).
Then when you want to get the grocery list, go to the Groceries page and modify your date range:
To plan for 2 weeks at a time (or more):
There are 2 ways to do this. If today is the first day of your meal plans (i.e. the day after your grocery shopping day), when you click "Regenerate week" you'll be able to generate both the current week and the week after, giving you two weeks at a time.
The other method is to create a week of meal plans that you like, and then save it from the "Diet actions" menu. Then you can load it into a future week, and then create a new meal plan for the current week for variety (or alternatively, just follow the same plan two weeks in a row. It will help minimize waste by a lot, and getting into a rhythm with a meal plan can make it easier to follow).
if you'd like to change your grocery shopping day, you can do so in your profile: