This example assumes you have an ISO image stored on an NFS volume.
Mount the NFS volume
mount -t nfs <Host Name or IP Address>:/<Path to Directory with ISO> <Local Mount Point>
Example:
mount -t nfs MyVolHost:/isodir /mnt
cd /mnt
Mount the ISO image
mount -o loop image-name.iso /mnt2
Create a local repository file and point it to the ISO image
vi /etc/yum.repos.d/local.repo
[local]
name=Red Hat Local Repository
baseurl=file:///mnt2/Server
enabled=1
gpgcheck=0
From here you should be able to use Yum normally with your local repository.