EVE-NG Community edition came with two options, OVA and ISO. The first option is to use OVA, which gives you the minimum installation steps required, given that you already have VMware Player/Workstation/Fusion, or VMware ESXi, or Red Hat KVM. The second option is to install it directly over a bare metal server without a hypervisor, this time using Ubuntu 16.06 LTS OS:
The ISO option, however, requires some advanced skills in Linux to prepare the machine itself and import the installation repositories into the operating system.
Oracle VirtualBox doesn't support the hardware acceleration needed by EVE-NG, so it's better to install it either in VMware or KVM.