I assume you have created *your* vdi (virtual disk) already? - Studio VM is my (not your) vdi.
If your left pane is blank you have to create your vdisk first - click on new and follow the wizard. Create your vdi big enough for the guest OS and pagefile - be generous.
The shared folder you have set up must be an everyone-share you can have many folders or use existing folders but do not use any 7-folders under /user - keep in mind these folders will show up as network folders in the guest OS (not sure which OS you want inside VB).
Access this folder from within 7? - open windows explorer and there you go...
Access this folder from inside the guest OS? - browse network, find those shared folders (should show up there) and...