Use the verb "be" as a helping verb when forming continuous tenses and the passive voice:

the present continuous tense:

• She is studying English. (main verb: study)
• We are going for a walk. (main verb: go)

the past continuous tense:

• Who were you talking to? (main verb: talk)
• Sharon was sitting all by herself. (main verb: sit)

the passive voice:

• She is helped by the teacher. (main verb: help)
• Tests are being done on the water. (main verb: do)

Use the verb "do" as a helping verb when forming negatives and questions in the present tense and the past tense:

present tense negatives:

• She doesn’t study English.
• The children don’t have shoes.

present tense questions:

• Does Maria study French?
• Where do they like to eat?

past tense negatives:

• He didn’t eat his breakfast.
• The project did not take long to complete.

past tense questions:

• What did you do with my shoes?
• Did the bus leave already?

Now try this exercise.  

Use the helping verb "have" when forming perfect tenses:

the present perfect tense:

• I have finally learned how play those chords.
• Kevin hasn’t eaten all of his breakfast yet.

the past perfect tense:

• They had never seen such a large fish
• It they‘d had more time, they would have remained.

with modal verbs that express the past:

• You should have helped her.
• That would have been great.

the present perfect continuous tense:

• Those children shouldn’t have been playing in that area.
• Vanessa might have been working late last night.

When a verb follows a modal verb, it’s in the simple form. Modal verbs change the meaning of the main verb.

• You should read more. (recommendation)
• They can read in English. (ability)
• She might read her book. (possibility)
• I must read the assignment. (necessity)
• He will read the newspaper. (future)

The subject of modal verbs is also explained in Yellow Level Lesson Ten.