The following is steps how to teach passive voice.
1. Prepare some pictures of people doing a certain activity e.g. someone reads a newspaper, writes a letter, eats an apple.
|the apple is eaten (detik.com doc)|
2. Ask students to call out things in the pictures.
3. Ask students to make a sentence. Give them an example: the apple is eaten.
4. Ask 5 students to write sentences made on the board.
5. Correct the errors.
6. Tell them the formula and the function of passive voice. It's better for you focusing on simple present. I will help students to understand easily. Avoid to explain more than one tenses.
7. Give students grammar exercises e.g. gap filling by omitting the past participle.