Click Share to bring up the "Share page to" window
There are two permission options available when sharing a dashboard page, "View" and "View and edit".
View lets users see the page but they are unable to change its settings.
View and edit lets users see the page and change its settings. Users are also allowed to take ownership of charts for editing.
In Dashboards, ownership of a chart is required to change its settings and components(filters, dimensions and measures).
Ownership is granted by opening a chart's settings menu and selecting "Transfer ownership to me".
You can now edit the chart.
Note that "Transfer ownership to me" is only available if the original owner has given you edit rights.