How To  Update Spray File

Assumption you have a file called tempdecal.wad.     (right-click on file and go into properties and check read-only on file)

First Locate Microsoft Windows File Explorer and Launch File Explorer,  should look like icon below

Start Steam if needed and go into Steam Library.

Find day of defeat game and right click on game and click on Properties

Now select "installed files" and then click on Browse. 

You should now be in windows file explorer in your installed directory for DOD.       My just select the DOD folder to change you location to look as follows: 

C:\Program Files (x86)\Steam\steamapps\common\Half-Life\dod

This is folder where your tempdecal.wad file must be copied into.     Backup or replace existing file.       Restart Game or Start it for first time and Decals should be changed.