Rule for changing voice from active to passive in simple past tense – 

Active VoicePassive Voice
Subject + Verb[past form] + object Object + was/were + Verb [past participle]+ by/to /with + Subject 

Examples

Active VoicePassive Voice
I knew him.He was known to me.
She bought me a dress on my birthday.A dress on my birthday was bought by her.
I helped them.They were helped by me.
I taught him math.He was taught math by me.
I read a novel.A novel was read by me.
The police rescued the child from being kidnapped.The child was rescued from being kidnapped by the police.
The boss gave him advice.Advice was given to him by the boss.
The chef made delicious meal for us.Delicious meal was made for us by the chef.
She consoled him for his loss.He was consoled for his loss by her.
I watched movies all day.Movies were watched all day by me.