How to use VBoxManage ?

Here is some examples (assuming the GuestAdditions has already been installed):
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VBoxManage import Win7Ent32.ova
VBoxManage list vms
VBoxManage showvminfo "Win7Ent32"
VBoxManage startvm "Win7Ent32" --type headless
VBoxManage controlvm "Win7Ent32" poweroff

VBoxManage modifyvm Win7Ent32 --vrde on
VBoxManage modifyvm Win7Ent32 --vrdeport 3389

VBoxManage sharedfolder add "Win7Ent32" --name vboxshared --hostpath /tmp --transient
VBoxManage sharedfolder remove "Win7Ent32" --name vboxshared --transient
VBoxManage export "Win7Ent32" -o Win7Ent32.ova
VBoxManage unregistervm "Win7Ent32" --delete