This article is based on openEuler 22.03, and I downloaded the full version.
Create a mount directory.
mkdir /usr/local/repo
Mount the file to /usr/local/repo.
mount -o loop /usr/local/everythingiso/openEuler-22.03-LTS-everything-x86_64-dvd.iso /usr/local/repo
Edit the file.
cd /etc/yum.repos.d/
Add the following content:
[openEuler]
name=openEuler
baseurl=file:///usr/local/repo
enabled=1
gpgcheck=0
Clean and rebuild the cache.
yum clean all && yum makecache
Test it.
yum install tar