If you are to install anything "from" pkgs.org, you must use the instructions provided in a package page.
Particularly in this link, you can see instructions saying to add third party repo:
This means you have to literally visit this page in a browser, then hunt down for RPM link of "nux-dextop-release" inside it, e.g.
http://li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-5.el7.nux.noarch.rpm then RPM install it.
Install nux-dextop-release rpm:
rpm -Uvh nux-dextop-release*rpm
You can either download the release RPM (aka repository configuration) and install it like pkgs.org recommends, but I prefer to skip the download step because
yum can easily do it:
yum -y install http://li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-5.el7.nux.noarch.rpm
Install paprefs rpm package:
yum install paprefs
Now you can just run that and it will install the package from the third-party repository resolving any dependencies as needed.
pkgs.org merely an aggregator/indexer for RPM/apt repositories and it does not host any RPMs.