Mount the iso to /mnt
In the case of redhat, copy the media.repo file from the root dir of the mount point to /etc/yum.repos.d. Edit the file and add the baseurl at the end as depicted below.
[root@mkoffer2 ~]# cat /etc/yum.repos.d/media.repo
name=Red Hat Enterprise Linux 6.3
* mediaid comes from the .diskinfo file located in the root of the DVD
This will allow installation of base packages. If you need non-base packages, you'll need to include the correct stanza in the media.repo config file.
Refer: redhat knowledgebase