Say you have a folder in the same directory as the DOSBox EXE called "blargh"
DOSBox uses virtual drives, so you have to "mount" them.
if you want drive C to refer to the folder called "blargh," you'd do this:
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mount "c" .\blargh
c:
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you can use any letter in place of C, and replace "blargh" with whatever game folder you want to refer to.
you can put all of that at the bottom of the autoexec file to mount them at startup so you don't have to remount them all the time, and just use the letter followed by a colon to switch drives.