What do you mean by "master" and "slave"? These terms are (to my knowledge) not used with NFS. I assume you mean that you have one server and two clients. On the server, you're going to need to set up an /etc/exports file that descibes which filesystem(s) are to be exported. If you have the NFS server installed, then typing "man 5 exports" will bring up the man page for the exports file which lists all of the options.
In general, an exports file looks like:
/directory/to/export host1(rw) host2(rw)
Once you've set up your exports start/restart the NFS server.
On the clients you can mount the filesystem as normal, assuming NFS client pacvkages are installed, e.g.
mount -t nfs server:/directory/to/export /mnt/server
To make the mount happen automatically on boot, add it to the /etc/fstab. There are a number of mount options -- see "man nfs" for details.
If you need more detail than this, you need to post which distro you're using (how to install packages and restart services varies from distro to distro).