Just run the installer, changing the discs as it asks. For the DOS games without a new installer, you will need to use DOSBox directly. DOSBox is actually fairly easy to use. For games that do not need to have access to its CD, nor any special configuration, the easiest way is to create a shortcut to DOSBox on your Desktop and drop the game's main executable on that shortcut. Some games will require more effort. Your CD drive will need to also mounted in DOSBox if your game require its CD. Some games will need to have its setup run, just as it needed in real DOS. Some games will require tweaking the DOSBox settings.
The most important thing to learn is how to mount drives. This gives the games running in DOSBox access to the files it needs. A couple of things to remember, Some games can be fussy about drive letters being contiguous, so it is usually best to mount your folder as "C:" and a CD drive as "D:". Never mount your entire real hard drive drive, always mount just a folder instead. Doing so can give the program you are running in DOSBox access to system files and the boot sector. Many DOS installers will try to alter these, not to mention older malware that may be in your old media.
For more information, read the manual or README that ships with DOSBox. Also, you may want to take a look at the official
60 second guide. You can also try one of the front end.
