The short answer I'm afraid is that you can't.
Zoom lenses which have a 'Macro' setting aren't true macro lenses and the desription is extremely misleading. A true macro lens is always a prime and is specifically designed to give at least a life size (1:1) image of the suubject on the film/sensor.
All that happens with a zoom lens with a 'Macro' setting is that when you select this setting all the elements of the lens move forward to enable a closer focusing distance than you would normally be able to achieve, but it wont be anywhere near the close focusing capability of a true macro lens.
Having said that, it's a useful feature to have in a walkabout/general purpose lens, and will probably enable you to get close enough to take close up shots of flowers and larger insects possiubly, like butterflies, but that's probably as good as it's going to get, but how close you'll actually be able to get will depend on the particular lens and how it's designed.
Keep moving closer to your subject and the point at which you can no longer achieve focus will be the closest you can get.