Hi Karla,
To show him that you are interested in going out, you could try baiting him with some goodies at work to get him to start a conversation with you.
For example, you could bring some kind of snack or beverage to share with your coworkers one work day and in the process of offering him a share of it, he may use that opportunity to start a conversation with you.
As long as you are receptive to the conversation, there is a good chance that he may either use that opportunity to ask you out or get your contact information.