1. Install Fedora repos
sudo dnf -y install https://extras.getpagespeed.com/release-latest.rpm
sudo dnf install fed2el-release
2. Install Virtualbox (from upstream Fedora 28 repos)
sudo dnfplus install VirtualBox
3. Install kernel-abi-whitelists
sudo dnf install kernel-abi-whitelists
4. Build necessary modules
akmods; systemctl restart systemd-modules-load.service
5. Rebuild modules automatically
You can enable service to automatically rebuild VirtualBox required kernel modules, after you upgrade to newer kernel:
sudo systemctl enable akmods