Important: Type FDREAD first in DOS to load the TSR that will allow you 
to read and write 1.8/1.9 meg disks etc.

Then read FDFORMAT.DOC for details.  But for a quick start just type
 
 FDFORMAT A:   

to format a disk in A: to 1.8 MB.  There are other larger or safer formats
you can do (read the FDFORMAT.DOC).