Choose between infinitve and imperative
First of all, to give instructions, the infinitive "choisir une option" or the imperative "choisissez une option" are both correct. The difference between the two comes from the nuance that it brings. On the other hand, in the same text, it is necessary to take care of the uniformity by employing the same mode everywhere.
Choosing an infinitive makes it possible to address a group of people more generally without aiming at a particular person. It has a more neutral and distant role. The third person is then used and the sentence can be prefaced by a polite phrase such as "prière de" or "veuillez" or simply "s'il vous plaît". The imperative, on the contrary, makes it possible to target a particular person and is much more direct by the notion of order that it introduces. The second person is then used and the polite mark is placed at the end of the sentence.
For instance, "déposer votre demande" is a general remark contrary to "déposez votre demande" which is more directive for someone.
Infinitive is perfect for short instructions like:
- instructions (eg: prière de garer la voiture)
- instruction guidance
- the steps to follow (as for electrical machine)
- technical indications (for example, in computer science)
- security rules
- instructions for use (eg: appuyer sur le bouton OFF pour éteindre l'appareil)
- cookbook (eg: ajouter du sucre)
- road signs (eg: défense de stationner)
Imperative is generally good to express:
- in job applications (eg: commencez par décrire votre parcours universitaire)
- in some forms (eg: faites parvenir ce formulaire par email)
- for safety posters where you want to directly target the target audience (eg: respectez le calme des résidents SVP !)