In written French, the infinitive is commonly used to give orders in an impersonal way. As opposed to the imperative, which commands specific people to do something, the infinitive issues neutral orders to unknown recipients in various documents, such as
En cas d’incendie briser la glace.
In case of fire break glass.
Suivre les consignes de sécurité.
Follow the safety procedures.
Avant de partir, fermer les fenêtres.
Before leaving, close the windows.
Ajouter une pincée de sel.
Add a pinch of salt.
It might help to imagine a phrase like Il faut or Prière de in front of the infinitive.
In negative impersonal orders, the two parts of the negative structure stay together in front of the infinitive.
Ne pas ouvrir la porte.
Do not open the door.
Ne rien laisser sur la table.
Do not leave anything on the table.
Ne pas manger ni boire
Do not eat or drink, No food or drink
Imperatives often include possessive adjectives (your children, your umbrella) that, in impersonal orders, must be replaced with impersonal alternatives, such as