First you need to designate a location to use as the C:\ root. I use C:\DOS\GAMES.

In DOSBox type MOUNT C C:\DOS\GAMES

You can follow that with -t dir
I also like to specify how much available space the program will see.
-freesize 400

MOUNT C C:\DOS\GAMES -t dir -freesize 400

Then to access a physical disc in drive D:\ you would type
MOUNT D D:\ -t cdrom

To mount a disc image located at C:\DOS you would type
IMGMOUNT D "C:\DOS\<disc.iso>" -t iso

Replace <disc.iso> with the filename.

Edit:
According to MobyGames, "Carmen Sandiego Word Detective" is a Windows or Windows 3.x game. This means it won't work in DOSBox without tinkering. See this guide.

Try a frontend like D-Fend or something, it takes most of that hard* technical computery stuff away.

* It's not hard, really. You need to understand the concept of a command line, and editing a config file in a text editor.

I do use D-Fend...

Okay, after I mount it, how do I install and/or run the actual game?

pariah164 wrote:

Okay, after I mount it, how do I install and/or run the actual game?

Type D:\ to access the disc.

You can see the files on the disc with the dir/p command. /p is a switch to pause the dir command if it fills more than one page.

The install file will have either an .exe or a .bat extension. Usually it's called INSTALL or SETUP.

I got an error when I tried to mount the iso.

"This operation is not permitted in secure mode."

I can't do anything in DosBox. Keep getting the secure mode error.

http://www.dosbox.com/DOSBoxManual.html

-securemode
Switches DOSBox to a more secure mode. In this mode the internal commands MOUNT, IMGMOUNT and BOOT won't work. It's not possible either to create a new configfile or languagefile in this mode. (Warning: you can only undo this mode by restarting DOSBox.)

It's probably a setting in D-Fend. Either disable it or use DOSBox on its own.

Managed to mount the CD, only to get 'This program must be run under Microsoft Windows' when I typed in 'Setup'.

It's not a DOS program.

So what can I do? Anything? 🙁 I am super discouraged.

If it's a Windows 3.1 game you can follow this guide.

If it a Windows 95 game You could try Virtual PC.

For either option you would need to install the operating system.

Virtual PC is not an option if he has Vista/Win7 Home.

Have you tried using the original CDs instead of the ISOs in Windows? Perhaps you didn't get the ISOs mounted properly.