The editor you refer to is now called Hammer, you can download it from
http://collective.valve-erc.com/index.php?go=hammer
It is also recommended to get hold of Zoner's BSP compiler tools instead of using the ones that come with Hammer.
There are loads of tutorials for building BSP files. If you are planning on loading them into DBPro, note that there are still some issues with BSP files in DBPro, collision etc. But these things are, as far as I know, going to be sorted in the near future.
"Man who looses key to woman's appartment...... He get no nookie" - A wise chinese man.