How do I transfer DBS Vickers shares from CDP?

I have recently bought some shares using DBS Vickers. However the shares are already transferred to my CDP account. If I sell my shares using DBS Vickers, does my shares in my CDP account get transferred to DBS Vickers and sold automatically? Or do I need to manually transfer the shares to DBS Vickers before I can sell?

If automatically will it be instant or take few hours to be transferred? And if it took few hours, will my dbs vickers be in negative value since the shares are still in CDP?