Jawaban:

The online classroom was not ready at that moment. Mr. Rudi, my homeroom teacher, instructed my class leader to create a WhatsApp group for our class. When my class leader had created the group, he added all contacts of our class members  Mr. Rudi into the group. After that, Mr. Rudi toldus that wehad an assignment from Miss Caca, our Biology teacher, to make a summary about virus and send it to her email when we have done it.

(the ones I bold is the one I change into the past tense.)

I'm sorry if the answer is wrong, I hope it helps.