First, make sure he knows you're available. If he asks if you're seeing anyone, and you're not, tell him. Guys worth their salt aren't going to ask out anyone who's in a committed relationship.
Next, don't wait for him to ask you out if you're into him! If you know he's also available find out what interests you both have in common. Is he into old school arcade games? Invite him to an arcade! Are you both bonding over your love for deep-fried food? Ask him out to your favorite bar for pub food and a drink. If he turns you down, stay chill. Maybe he has something he has to do that day or isn't really into the idea you threw out. Just say something like "Well, I'm also free Friday afternoon if you want to do something." Balls in his court and if he makes an effort to get together you'll know he's into hanging out with you. If not - next!