Temporary
If you want to make a temporary use of a NSF, just issue:
mount -t nfs host:/path/to/nfs /mnt/dir
To disconnect issue:
umount /mnt/dir
Permanent
If you want to have a permanent connection (i.e. every time the system reboots), edit /etc/fstab and add:
host:/path/to/nfs /mnt/dir options
More:
http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/custom-guide/s1-nfs-mount.html