iPad - Navigate to the recipe and tap the Edit button. Scroll down to Categories and tap it to choose the categories for that recipe. Alternatively, tap the info button on the right side of each recipe row in the main recipes listing.
iPhone - Navigate to the recipe and tap the Edit button. Scroll down to Categories and tap it to choose the categories for that recipe.
Mac - Navigate to the recipe and click the Edit button in the upper right corner of the screen. Press the Edit Categories button to choose the categories for that recipe. Alternatively, you can drag and drop recipes into categories from the main recipes listing.