You might try entering the death certificate under the evidence box in the Death Event.
Just click on the last little box on the right side of the line for the Death event and a Proof Screen will appear. Click either "New" or "Existing" depending on wheather you have the "Death Certificate" source in your file yet. Either select the existing source or enter the data into a new "Death Certificate" template.
Click on the "Footnote" radio button and select "All Evidence" or "selected Evidence" for the footnote and the data on the death certificate will appear as a footnote in your printouts.
Normally a death certificate is not a separate event, it is proof of the dath event.