Usually the past participle does not change when conjugated with AVOIR but if there is a preceding direct object then the participle has to agree. e.g Les lettres que j'ai reçues.

Explanation

Les lettre = feminine + plural precede the verb, therefore, past participle also has to feminie + plural.

The Past Historic is a past tense used for recounting past events, usually in novels and stores. Therefore you only need to recognise it, not use it yourself. If you read a French novel as part of your A2 course or for coursework, you will soon get used to it.

For example