At the top right of the dashboard is a lock icon. Click this to enter edit mode.

When in edit mode a few things change. Each widget section gains an Add New Widget button and each widget gains a Remove button.

Clicking Add New Widget will present you with the widget selection dialog. Here you can select the type of widget you want to add.

If you have the Create Dashboards permission, then you will see an add button to create a new project dashboard from the current dashboard configuration. Clicking the lock again exits edit mode.

If you have the Create Dashboards permission, the top bar will look a little different for project dashboards. You can click the name of the dashboard to edit it's name. You can add a new project dashboard using the current configuration as a starting point. You can save the changes you've made. You can delete the current project dashboard. You can toggle whether filters should be retained so all users will see the same filtered view for this project dashboard.

If you have the Create Dashboards permission and you make a change to a project dashboard while not in edit mode, such as which property is displayed on a widget or changing the filtering. A save button will be available for you at the top right to save those changes without having to go into edit mode.