Maybe you made a handful of changes to your settings and want to rebuild the whole weekly meal plan at once. Or maybe you just really hated the meal plan. You can rebuild the whole week by clicking "Regenerate entire week" at the top of the planner page (this is a premium-only feature).
The planner takes about 20 seconds to run, and will clear the existing meal plans on whatever date range you select. So before you do this, maybe go through the meal plan you started with and thumbs up/down any foods you do or don't like, and set things that you really like to reacur often in specific meals. Then have it start generating.