Hi! Welcome to the Pentax Forums!
Do you have a copy of the K-5 manual? It is a good first step to understanding your camera's features. The PDF version of the manual is available for download from Ricoh/Pentax at the link below:
http://c2b6d376b97bcc466063-5420c200a1f030d1394a9548df6eadbd.r5.cf2.rackcdn....5%20manual.pdf
As for your light meter, EV (
Exposure
Value) is just a way of expressing exposure. The meter works in much the same way as the one on your film camera did and requires no special treatment or attention. One EV unit is essentially the same as one "stop" of exposure and can represent either aperture or shutter speed or ISO sensitivity depending on your exposure mode. With your camera, you can apply EV compensation and bias the exposure either side of the recommended setting to compensate for strong back-lighting and such.
I hope this is helpful.
Steve
P.S. There is an extensive article on EV in the Wikipedia...probably more than you ever wanted to know
Exposure value - Wikipedia, the free encyclopedia