The negative and the question: нисам, ниси…
Ten minutes on saying it didn't happen: the negative fuses бити's own short forms into one word - нисам, ниси, није, нисмо, нисте, нису - with no separate не anywhere, and a yes/no question is just да ли in front with nothing else moved. Build three negative sentences, hear that a message was never seen, and reuse the question rule you already know from the present tense.
The part of the grammar page this lesson drills — read it here, then use it.
Saying it did not happen
The negative uses the fused forms you already know from бити - нисам, ниси, није, нисмо, нисте, нису - followed by the same participle. Нисам радио means “I did not work”; there is no separate не here, exactly as in the present tense.
To ask a question, put да ли in front and leave the rest alone: Да ли си радио? Word order doesn't change - same rule as in the present tense.