How do you change past simple to Past Perfect?

Related questions

1. What is the difference between simple past and past progressive?
2. What is the past tense of sleep?
3. What is past perfect and past simple?
4. What is rule of past perfect tense?
5. What is the rule of past perfect continuous?
6. Where do we use past perfect tense?
7. What is the difference between past perfect and past participle?
8. What is structure of past perfect tense?
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10. Why we use past perfect continuous tense?

Tags

1. #remove
2. #second
3. #putting
4. #expression
5. #perfect
6. #simple
7. #present
8. #participle
9. #cases
10. #before
11. #change
12. #tense