Add or change a clef
You can add a new clef by going to the "Measure" toolbar, clicking on the Clef tool and choosing the new clef. If there is no range selection, the new clef will be applied until the next clef or the end of the score. If you only want to change the clef on specific measures, make a range selection of the measures before choosing the clef.
You can change an existing clef by clicking on the clef and choosing the new clef, or using the tool available in the "Measure" toolbar.