Recall that one of the principal distinctions in French between le passé composé and the imperfect is that the former describes an action that occurred at a discrete time in the past, whereas the latter describes a repeated or habitual action over an indefinite period in the past. So:

"I put on a tuxedo last night."
"J'ai mis un smoking hier soir."

But:

"I used to put on a leather jacket when I went to high school."
"Je mettais un blouson en cuir quand j'allais au lycée."