To make source that its rpm-packages in local disks

Add Disk-based sources
Fist,make a folder,e.g. /media/baserepo.
Then make soft-links from linkers in the folder to all the rpm-docs in CDs.
ln -s /mnt/iso/Fedora/RPMS/*.rpm /media/baserepo
Third,yum install createrepo(in fact createreop is in the CDs)
And,the next step is createrepo /media/baserepo
After this,there will be a new folder named /media/baserepo/repodata and this is just the data-source document of yum.
Finally edit yum:add sentences bellow.

[local_base]
name=iso
baseurl=file:///media/baserepo
enabled=1