我买了~还没拆封~等这两天把游戏打完就准备重装系统换Win8用~到时候上评测...

There are two ways to left-click and drag.
The first is to use your thumb to click the button, then while holding the button down, to use your finger to select the object and move it, releasing it with your thumb. After a little practice I think this will become second nature - and I think is the way Logitech intended it to work.
In one of the more recent releases of the driver they've also enabled a second double click drag mode. In this case - you double tab the object, and on the second tap hold your finger down - then you can move the object. This is how most laptop touchpads work today - so will be familiar to most.