I have learned that in using the past perfect tense of the verb

Answer:
you use the past tense of the verb "to have," which is had, and add it to the past participle of the main verb. For example: subject + had + past participle = past perfect tense. Past perfect tense will be useful for you. This verb tense allows you to discuss or write about an event that took place in the past, but before another past action.