In Theme > Kitchen set Show Allergens, Show Dislikes and Show Diet Preferences to Yes. Each one adds the matching section to the customer's My Preferences area on their profile and to the preference sidebar on ordering pages. Show Allergens and Show Dislikes only appear as settings (and only work) when the Allergens & Dislikes module is active; Show Diet Preferences (meal categories the customer prefers) is always available. If all three are No (or off because the module isn't active), the preferences panel is hidden entirely.