I know this post is a little late, but it seems you have to either manually install it in CentOS, or, and a better way, is to go the
PlayOnLinux rpm website and install the rpm package provided there. There is also a pre-configured repo config file for dnf there as well, so you could copy that to the
/etc/yum.repos.d/ directory/folder.
If you don't want to add the repo file, you could just type something like this to directly install the rpm package from the PlayOnLinux website directly,
Code:
dnf install http://rpm.playonlinux.com/playonlinux-yum-4-1.noarch.rpm
The benefit of adding the PlayOnLinux repo to dnf's repolist is that you in that case could just type something like the following instead,
Code:
dnf install playonlinux