Select your video+audio clip and either hit the 'un-group' icon (the un-linked chain) or use ungroup from the 'Edit' top menu. This info and more is available if you use the inbult help facility, [F1] key, and search for 'ungroup'.
It is in the pdf manual which was installed with the software, there is a link to on your start menu for MEP under Magix, Movie Edit Pro(version), Documentation.