You can delete any recipe that is saved in your account. It doesn't matter whether you have created the recipe from scratch, or found it in the recipes database.
You can click here to open the recipes page. Alternatively, follow these steps.
Step 1: Log in to Mealplana at https://app.mealplana.com
Step 2: Click on Recipes
Step 3: Find the recipe you want to rename, then click on the three dots on the right to open the actions menu.
Step 4: Select Delete from the dropdown menu
Step 5: When you are sure you want to indeed delete the recipe selected, click on Confirm Delete. This action is irreversible.