There isn’t a separate macro mode to switch on. On this lens, “Macro” means it can focus relatively close, not that it has a special macro function.

To get the strongest close-up effect, zoom toward the long end and focus at the lens’s minimum focusing distance. That gives you the maximum magnification this lens can provide.

However, this lens is not a true high-magnification macro lens. Its maximum magnification is about 0.26x (roughly 1:4), which is much lower than a dedicated 1:1 macro lens. So it’s fine for close-up photography, but limited for very small subjects.

Extension tubes could increase magnification somewhat, but because the lens is already relatively slow at the long end, they may make it too dim to be very practical.

So the short answer is: nothing to activate—just use the closest focusing distance available, preferably at the telephoto end, and treat it as a close-up-capable lens rather than a dedicated macro lens.