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To get a copy of the appropriate repository file for your system, see https://shibboleth.net/downloads/service-provider/latest/RPMS/ for a simple drop down form that will generate a copy for you. Per the note above, RHEL 7 systems must use the CentOS 7 repository.
If you run into problems, the best first step is to repeat that step and see if you need to make any adjustments to the repository definition to deal with whatever transitory issue(s) might be affecting the situation. If that doesn't work, it's very likely that there's nothing wrong the project can fix, and you should expect a response to that effect if you ask. If anything could be done, it already would have been.
Installation varies by OS, but usually you just drop the definition file into a directory such as /etc/yum.repos.d. You can turn the repository on and off by adjusting the "enabled" property in the file, such as to prevent automated updates and maintain manual control. While enabled, the yum command will "see" the Shibboleth packages when you perform standard operations, and installing the SP should require only a single command:
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