I don't know about this game particularily - it appears you found some of the earlier details people posted - but I think there are "how to get nfsse working in dosbox" info out there, so hopefully your search is going well on those fronts.
But, we can probably get dosbox to cooperate with you.
In the .conf file, you can create an [autoexec] section, or perhaps one already exists. You can put the same info in that section that you type at the dosbox z:\> prompt, so you can try things until they work, then put them conveniently in in autoexec.
To get the ISO file mounted, use this command (at the dosbox z:\> or c:\> prompt, or in autoexec section of conf, it's all the same):
IMGMOUNT D C:\Images\MyImage.iso -t iso
That will make the iso file the D:\ drive.
Of course, your c:\images\*.iso path will be whatever it actually is for you. It doesn't matter what directory it's in, though it's helpful if there are no spaces.
You'll probably want to mount a directory as the dos c drive as well, if you haven't already:
mount c c:\games
or whatever games directory you have or want to create.
then, if all goes well, you can install from the "cd" d: drive to the "hard drive" c: drive inside dosbox and it will work - or get closer to tweak more, at least.
If I recall correctly, NFSSE (or some NFS) was somewhat picky but certainly able to run successfully in dosbox, so hopefully you can get it figured out with our (or other people's!) help. Just keep posting your details and the steps & results you're currently getting!
And as Tien said, welcome! Glad you found us. We'll do what we can.