Refer to the Making Custom Sounds tutorial for more details on that subject.
After you have a sound in the right format, whether you make a custom sound, or find an already made sound, you must put it in the right folder. Make sure that the sound is 8-bit mono, otherwise it will not work properly, or might just not work at all. WAV format, which most of them usually are. Half-Life is very specific in its sounds format. The only difficult part is supplying the sound. When the player steps on this platform, you want it to make a sound. What if you wanted to add your own music or sound effects into the game? Well, we can do this simply through the ambient_generic entity. As we map for Half-Life, we usually don't have to add any audio effects, since we are mapping for an already coded game. There are the visual effects and the audio effects, both equally important.
Obviously, there are two main components to a game.