To insert elements that already exist in your model, just drag them from the Tree View and drop them where you want them to be in your diagram. You can always move elements around in your Diagram using the Select Tool
Per inserir elements que ja existeixen en el model, simplement arrossegue- los de la vista d' arbre i deixeu- los anar on vulgueu en el diagrama. Sempre podeu moure elements en el diagrama usant l' eina de selecció