How to read:
follow the wiki above and look in beer/equipment/hydrometer.
A trail jar.
Or something deep enough to fit the hydrometer in but narrow enough not to waste loads of wort. Or just float it in the container it's in.
Don't forget to adjust for temperature.
if your short on the basic and need I injection of knowledge then a look at www.howtobrew.com
will do wonders.
But any emergency questions then you've already found the quickest way. Just ask.