How to Use a Fluke IR Heat Probe?

Hi Friends,

As I know that temperature is typically measured using a mercury thermometer which consists of a glass vial containing liquid mercury. Temperature changes lead to expansion and contraction of the mercury liquid which can be read off a scale. In the use of a fluke IR heat probe, some time I am getting confuse on it. So, anyone having brilliant idea on it, then please suggest me for which I can use it in properly manner.

Thanks a lot!
Steven Brooks