This method works for just any commercial business in the world. Let's use "Dubline Jacks" as our example.
1. Type "Dublin Jacks Hong Kong" into google.
2. You will probably notice either (a) the website for the very place you are trying to find or (b) it referred to by some other website. In our case we don't even need to click on any links because the address "27 Cochrane Street, Central" comes up in the text of the very first item listed on google. Anyway, within 2 or 3 minutes, you will have most probably found the address.
3. Go to an online map website for the city you are in. In the case of Hong Kong, I usually use www.centamap.com
4. Type in the address in the map's search facility. In the specific case of centamap, you can click on "English" if you don't read Chinese and then enter "Cochrane" into the box and click "Search".
5. I think you know what to do from here.
In the specific case of Dublin Jacks, it is at 27 Cochrane Street, Central. Cochrane Street is a north-south running street that goes uphill to the south (as does just about everything north-south running street in the north part of Hong Kong Island). Dublin Jacks is on the right side of the street as you walk uphill (that's the west side). It is in the stretch of Cochrane Street that runs between Wellington Street (to the north or downhill of Dublin Jacks) and Lyndhurst Terrace (to the south or uphill of Dublin Jacks).
From MTR Central exit D2, take exit, immediately turn right, walk about 20 metres to Theatre Lane, turn left into Theatre Lane. Walk about 50 metres to Queens Road (that great big main road that runs east-west through much of Hong Kong). Turn right into Queens Road, and walk about 250 metres to the start of the midlevels escalator. Take the mid levels escalator and that eventually runs directly above Cochrane Street. I'm presuming you can get off the escalator at some appropriate point.
I don't know, because I've never even been there. Yes, I am a Dublin Jacks virgin...