I bought a cheap open reel surveyors type tape measure, but I'm not sure
how to use it.

Top part has a handle grip section, and at the opposite end is a kind of
pointer.

Like this:

http://bigslickdeals.com/images/cham...apemeasure.jpg

One side of the tape measures in feet and inches and zero is at the tape
end. Other side measures in metres and cm but zero is about 32cm from
the end of the tape.

How am I supposed to use this tape meaure. In particular, I cannot
fathom how to use the metric side of the tape measure. Thanks.