You can usually find these rotating (hard to miss) terminals at the landing point on zCS Sims, for example Sea Fortress.
You will receive a box within a couple of seconds if Second Life is in a good mood, terminals are networked and all deliver the same box.
You must now unbox the system. The easiest way to to unbox is to right click the box in your inventory and click add. You will shortly find a new folder in your inventory and the box will detach.
There are two main parts to the meter, the hud and meter itself, both will be in the folder you just received. You will need to wear both, right click them and click add. The system will begin booting, this takes only a few seconds.
If everything is how it should be, you will now see an extra interface on your screen similar to the one below.