Past perfect

Past perfect is used when you need to express an action taking place in the past, as the name says.

So the structure is subject+ had+ verb+ rest of the sentence

The verb must be in past and if it is an irregular verb the verb must be in past participle form. 

Remember there are some exceptions for some regular verbs.
For example if you use love, you can not  conjugate it like loveed, you just put a "d" and write loved.

Source: https://www.ego4u.com/en/cram-up/grammar/past-perfect-simple

SO BE VERY CAREFUL WITH THAT


Exercise!!
Find the sentences with past perfect.

The second appearance of the ghost was on Sunday night. Shortly after the family had gone to bed they heard a fearful crash in the hall. A suit of armour had fallen on the floor and in a chair sat the Canterville ghost and rubbed his knees, which seemed to hurt. When the twins started shooting peas at him with their pea-shooters, the ghost stood up with an angry growl and passed through them like a mist. He also blew out the candle, leaving them all in total darkness. On top of the stairs the ghost turned around and, in order to frighten the Otis boys, laughed his most horrible laugh. Just then, a door opened and Mrs Otis came out of her bedroom. “I am afraid you are not well,” she said, “I have therefore brought you this bottle of medicine.” The ghost looked at her furiously, and then he disappeared.

When he reached his room, he was completely exhausted. This American family was extremely annoying. But what annoyed him most was, that he had not been able to wear the suit of armour. The weight of it had made him fall and hurt his knees.

For some days after this the ghost only left his room to renew the blood-stain. However, on Friday, the 17th of August, he tried to frighten the Otis family again. At half-past ten the family went to bed. For some time the ghost heard the twins laugh, but at a quarter past eleven all was still. So, at midnight he left his secret chamber and glided through the corridors, when suddenly, behind one corner, a horrible ghost stood right in front of him. As the Canterville ghost had never seen another ghost before, he was terribly frightened. He quickly hurried back to his room. But then he thought that he should go and and speak to the other ghost. After all, two ghosts were better than one, and his new friend might help him to frighten the twins. However, when he came back to the spot, he found that this 'other ghost' was not real, but only a white sheet which the twins had hung there to play a trick on him. Very upset the Canterville ghost went back to his chamber.

Source "The canterville Ghost" chapter 4