Morning oscar!
there’s no official procedure in the docs for that but you may start reading this section in the docs to know how you can add content to your cloud.
If you want to import a vmdk file and you want to use it for the KVM hypervisor I’d start converting the VMDK file to qcow2 using qemu-img (you may find this information useful). If you want to import a Windows VMDK file you may find this post useful..
Once you have the qcow2 file you can upload it to the image datastore as explained in the Managing Images section. Then you should create a template which uses that image and instantiate the template to launch the VM.
Cheers!