How do you change active and passive voice?

Starting with a sentence in the active voice, you change the object into the subject. Then you add the verb "to be" in the appropriate tense before the root verb. You can add the former subject after the Word "by"

E.g. "John hits Jim" "Jim" is the object, so he is now our subject. We add the present tense of "to be", which in this case is "is" and the root verb "hit" and "by" followed by the former subject "John". The sentence reads "Jim is hit by John."

In the past tense "John hit Jim" becomes "Jim was hit by John". In the future, "John will hit Jim" becomes "Jim will be hit by John."

A more complicated example: "The revolutionary tribunal sentenced the poor man to five years hard labour." becomes "The poor man was sentenced to five years hard labour by the revolutionary tribunal."