pbase-preconfig-virtualbox package install the dependencies and adds the
KERN_DIR and KERN_VER environment variables required to run VirtualBox and build the guest extensions.
yum -y install https://pbase-foundation.com/pbase-repo.rpmyum -y install pbase-preconfig-virtualbox
Reboot after doing this to load in the new environment variables. Then when running in VirtualBox guest you may select the "Insert Guest Additions Disk" and accept the run prompt.
If your intention is to run VirtualBox host