How to deploy Ubuntu Core from KVM to VirtualBox?

Steps:
1. Download Ubuntu Core of KVM image from URL below:
https://developer.ubuntu.com/core/get-started/kvm

2. To decompress xz.

3. To convert the format of img to the vdi via VBoxManage command below:

VBoxManage.exe convertdd ubuntu-core-16-amd64.img ubuntu-core-16-amd64.vdi

4. Import vdi file above to the VirtualBox without issue.