To have expresses necessity due to circumstances.
Our fax-machine did not work and I had to go the accounting department to send him a fax message.
Наш факс не работает, и мне пришлось пойти в бухгалтерию, чтобы отправить ему факс.
To have can be used in all the tenses of the Indefinite group and occurs in the Present and Past Perfect tenses as well.
I'll have to get up early tomorrow.
Мне придется встать завтра рано утром.
Have you ever had to translate business talks?
Тебе когда-нибудь приходилось переводить деловые переговоры?
Note: When the verb to have is modal it takes the auxiliary verb to do to form it's negative and interrogative forms.
I don't have to get up early now.
Мне теперь не придется рано вставать.