For Counter-Strike 1.6 [with steam]

Unzip the ZIP file to somewhere you can find it (Desktop recommended).
when unzipped, you will have 2 files, one is a BMP of the spray (for you to have, you don't need it though) and the other is called PLDECAL.WAD.

First thing you need to do is rename the file PLDECAL.WAD to TEMPDECAL.WAD.

Then all you need to do is place this TEMPPLDECAL.WAD file into your CSTRIKE folder.

Being version 1.6 though, it is located in a different location from 1.5, see below:

EXAMPLE: C:\Program Files\Steam\steamapps\your@emailaddress.com\Counter-Strike\cstrike

**NOTE **

If at any time you go into the Options section in the game, your PLDECAL.WAD file will be reset, and you will have to put the PLDECAL.WAD/TEMPDECAL.WAD file into your CSTRIKE folder all over again.

To avoid this from ever happening, when you install the TEMPDECAL.WAD file, right-click on it, select Properties and check the box labeled "Read-Only". Click Apply, then OK. Your spray still won't display in the customize screen, but at least now it won't be reset.