If you want to install a package like Docker Community Edition on OEL, you'll have to add the CentOS Extras repo, which as of release 7 is built-in to CentOS and not added on later like EPEL is. As a result, instructions for adding it to EL7 are hard to find. This should work for any build of Enterprise Linux that does not already include the CentOS Extras repo. I have absolutely no idea if it's apporpriate to use this repo on a build of Linux other than CentOS, but it should be.
This was tested on Oracle Enterprise Linux 7, but should be copy-pastable on any version or EL build assuming things don't change too much.
# Get OS Release number