Use 'screw around' in casual conversations, not in formal or professional settings. They won't hire you if they think you just screw around all day.
Pro Tip 2/3
Negative Connotation
'Screw around' often implies disapproval of someone not doing what they're supposed to do. My boss got mad at me for screwing around when I should have been working.
Pro Tip 3/3
Playful Tone
Sometimes, 'screw around' can be used in a playful, light-hearted way among friends. We spent the whole afternoon screwing around at the arcade.