FALLOIR to be necessary
Falloir is an unusual verb as it exists in the third person singular only, with 'il', meaning 'it'. It is therefore an impersonal verb. The general meaning would be 'it is necessary', but sometimes we can translate it as 'we must'. It is an irregular verb. You will see from some of these examples that we can use the indirect object pronouns me, te, lui, nous, vous and leur to make the meaning clearer.
Il faut It is necessary.
Il faut partir ce soir. - We must leave this evening.
Il leur faut une voiture. - They need a car.
PERFECT TENSE - PASSE COMPOSE
Il a fallu It was necessary, it has been necessary.
Il a fallu retourner en ville. - We had to go back to town.
Il vous a fallu vendre la maison. - You had to sell the house.
Il fallait It was necessary, it used to be necessary.
Il fallait toujours faire une reservation à l'avance. - It was always necessary to make a reservation in advance.
Il nous fallait une maison plus grande. - We needed a bigger house.
Il faudra It will be necessary.
Il faudra prendre l'autobus. - We'll have to go by bus.
Il te faudra passer un examen. - You will have to sit an exam.
Il faudrait It would be necessary.
Il faudrait prendre l'autobus si la voiture tombait en panne. - It would be necessary to take the bus if the car broke down.
Wherever possible, we can use the infinitive after 'il faut'. If we have to use 'il faut que', it must be followed by the subjunctive.
Il faut que les enfants sachent nager. - The children must be able to swim.
Il faut que tout le monde puisse entendre la musique. - Everyone must be able to hear the music.
THE INFINITVE FALLOIR
It is possible to use the infinitive falloir after the verb aller (to go) for the near future, with the meaning 'It's going to be necessary to...', for example:
Il va falloir garer en dehors de la ville. - It's going to be necessary to park outside the town.
Il va falloir acheter une lave-vaisselle. - It's going to be necessary to buy a dishwasher.
There may again be instances when we have to say 'Il va falloir que...' followed by the subjunctive:
Il va falloir que nos amis nous accompagnent en ville. - It's going to be necessary for our friends to accompany us into town.
Although it is irregular, falloir is not a difficult verb to use because you only have to learn the form of the third person singular, il. The alternative is to use devoir, which means must, have to, ought, or should, but this again is an irregular verb and is not a straightforward one to learn, so if you can remember to use 'il faut...', it should be much easier to do so.