as a verb, 'stress' means to emphasize or place importance on something. 'Stressed' is the past tense, indicating that the action of emphasizing has already occurred.
She stressed the need for punctuality at the meeting yesterday.
The teacher stressed the importance of completing homework on time.
He stressed that safety should always be the top priority.
ensure that 'stressed' is not being mistaken for its adjective form in the sentence. Context usually helps in distinguishing the two. 'Stressed' as a verb is often followed by a direct object or a 'that' clause, as seen in the example sentences.