first of all, copy the files into a new folder in C: , preferably dbase,(it will make it easier to find, also keep it less then 8 letters long).
If the DBASE is a true dos based utility then you would need to Shutdown and restart in DOS, then at the prompt type
dir +press enter
cd dbase +press enter (or whatever you have called the new folder)
look for the install or setup file,
type install or setup, hopefully this will install the app and you should then be able to run it by typing its name,
if it doesnt have an install or setup but has a file with a exe extension then try typing that eg. dbase.exe, just type
dbase +press enter
Hope this helps
ps i presume you have tried it in windows 98, if not then try it in windows first.