After selecting your project or a new one, you get the standard form for general settings. After that page you see the template selection, here you can select a custum made one or create your own. If you already created one yourself than you can edit this with the edit button on the right. The menu and way of handling templates is different in v10 than in v9.

Take good care that you have the correct setting in the pulldown menu's above in this screen or you will not see your custum templates.