If you would like to play free Jedi Knight levels, it's simple. First you need to download one (or many!). You can get them right here at 3D Gamer's Edge, or go to my Links page and find some on other sites.
Download the file(s) onto your hard drive. On my computer, I've created a 'Download' folder, with a 'Jedi Knight Maps' folder in it, just for this purpose.
Now you will need to unzip the file. You can use WinZip for this. If you have it, just double click the downloaded level file and WinZip launches itself. If you do not have WinZip, you can get a free 21 day trial version at WinZip.com. When WinZip asks you what folder to unzip it to, click select a different folder..., and navigate to your LucasArts/JediKnight/Episodes folder. Now unzip the file.
When done, go to the LucasArts/JediKnight/Episodes folder, there should be a read.me file and the map file located within. Read the "ReadMe.txt" file, as it will usually contain the level's story, known bugs, and other useful information.
There, now you're ready to play your free level!
Next, just launch Jedi Knight. When it's up and running, go to 'Single Player', then 'New Game'. In the Episodes box, look for the level that you would like to play. Click it, and click 'OK'. The level will begin loading, and you're on your way! Enjoy the FREE level!