Introduction: Dosbox Video Tutorial for Playing Games
Here's a quick list of what you'll need to play old DOS games on your new PC:
An old game.
Follow the instructions in my video (turn on annotations) to see how to mount and play games or check out this link.
You may need to modify your config file to get games to run smoothly. I found that on my pc I needed to up the number of CPU cycles by quite a bit to get things to stop being choppy.
Also, if you're looking for old games, check out Abandonia for a huge selection.