You can change your default dashboard in two different ways:
To change your default dashboard, click "Manage Dashboards" under the Dashboard tab.
Once you're in the Manage Dashboards tab, click on the triple-dot menu next to the dashboard that you would like to make your default dashboard. Select "Make My Default" to change the default dashboard to the one that you selected. This will then make the selected dashboard your default dashboard.
2. Change your default dashboard from Settings > Account Settings > Default Dashboard. Select from one of the dashboards in your account from the drop-down to select a new default dashboard.