PRESENT & FUTURE actions
Use SHOULD + verb to give advice / make a suggestion / express obligation
You should eat at least 5 fruit & vegetables every day.
You shouldn’t go to bed late before an exam.
PAST actions
Use SHOULD HAVE + PAST PARTICIPLE to express regret / criticism
Examples:
I should have studied for my English test. (Meaning: I wish I had studied)
You shouldn’t have told him about the party. (Meaning: I wish you hadn’t told him about the party).