Go to the editing (advanced entry) of the record in question by pressing the blue chevron (1) in the “Details/Edit” column, then press “Change Type” (2).
Choose the type of publication (1) in which you want to convert this publication. The “Before” (2) and “After” (3) fields allow you to see the changes that will be made during the conversion. Once you are sure of your choice, click on “Continue” (4).
Adapt the metadata to match the new type selected. Then click on “Save” to save the type change and metadata changes.