How to Propose a girl at office?

I like one girl in the office she is in different department, when I see her she also look at me and never removes her eyes from eyes until I do it. I think she is interested in me but I don't know how to approach as I never spoke to her yet.In case she is making fun of me and complains to the HR that I proposed her, I might loose this job so please help. How to get her in my arms?