The English word, must or the phrase to have to can be expressed two ways in Spanish.
tener que and deber
Pablo tiene que levantarse una hora antes que nosotros para no llegar tarde a la oficina.
Pablo must get up an hour earlier than us so he does not arrive late at the office.
Here are some other example of various sentences with different conjugations of tener que.
Tengo que aprender lo mas que pueda..
I must learn as much as I can.
Tengo que preparle eso.
I must prepare that for him.
Tuve que llevar a mi hijo al hospital
I had to take my son to the hospital.
or one can use deber to express the same idea
Debo preparle eso.
I have to prepare that for him.
Debo llevar a mi hijo al hospital
I must take my son to the hospital.
I must do it.