Melissa McCarthy, at the Los Angeles premiere of “Bridesmaids” last month. (Chris Pizzello/Associated Press)

That’s how Melissa McCarthy — one of the stars of “Bridesmaids,” the not-at-all chick-flickish, very funny movie that opens tomorrow — describes how she was able to attempt stand-up comedy for the first time.

I recently chatted with McCarthy, who also stars on CBS’s “Mike and Molly,” to write a Sunday Style profile. During our conversation, she recalled her first experience with stand-up — an experience that eventually led her to join Los Angeles improv group the Groundlings (where she worked with “Bridesmaids” co-stars Kristen Wiig, Maya Rudolph and Wendi McLendon-Covey) and kick-start a career as an actress. It all began 20 years ago at a Manhattan open mike night, to which McCarthy came, at a friend’s urging, with absolutely zero material prepared.

“I didn’t prepare anything because I didn’t know how to do it,” McCarthy recalled.

Read more, and watch a clip of McCarthy in “Bridesmaids,” after the jump.

“So I just showed up that night and did it. And I was like, this is really fun. Making a room full of people laugh is a really good deal.”

McCarthy continued:

“I’m from Plainfield, Illinois. We didn’t go to comedy clubs. I guess I just thought, if you’re funny, you get up there and see if you can do it. So I just got up there and talked about random stuff.

“I talked about my day. And I had this crazy wig on and I looked insane, but it went really well.

“I didn’t know what the light was for. It was the worst thing. They kept flashing the light in the back of the room. Which, every time they flashed it, I thought they were saying, ‘You’re doing great!’ So I’d launch into another story. But it was supposed to be like three minutes, and I think I did, like, 10. Now I realize, oh my God, you don’t do that! You do not do that. That’s, like, a cardinal rule.

“I got off [stage] and they actually asked me back. But [the manager] said, ‘If you don’t listen, if you don’t pay attention when I flash that damn light at you, you will never work here again.’ I was like, ‘I thought you were saying keep it up.’ ‘The light means get off the stage.’

He was so mad at me. And I was like, ‘I didn’t know. I didn’t know.’ ”

Clearly, McCarthy learned. And now she’s able to apply those important comic lessons to finding the humor in movie scenes like this: