Hi Johnson,
Good question! I haven't really hired anyone yet, but I know that you can post your ad on many sites offering online jobs, you can try craigslist for example or maybe there's a site for Singaporeans so you can hire locally :)
You might want to consider your employees - job description/scope and the pay (basically the employee contract). Also, before you post the ad it might be best if you can check if you can afford one, like are you making more than enough profit? If business is booming, having a working staff would be great - Customers just love great customer service :)
You might find the discussion in this thread helpful - Link hidden: Login to view
Hope this helps, cheers :)