In the DOSBox 0.74 folder, there is a configuration file called dosbox-074.conf. This can be edited with any text editor. At the very end of the file, there's a section containing auto-exec commands, like a batch file, that will run every time you run DOSBox. That's where I put my mount command. I have my DOS folder on the C drive, thus my mount command needs different code than Simon's.
[autoexec]
# Lines in this section will be run at startup.
# You can put your MOUNT lines here.
mount c c:\users\ryan\dos\
c:\
cycles=max
Ryan