You need to be in edit mode in order to manage dashboard layout. Click on "Edit" in top dashboard menu to activate edit mode.

You can modify Dashboard layout to your needs by:

Adding rows

Scroll to the bottom of the Dashboard and select number of columns you require in the new row.

add-row

Changing size

Point your mouse among two dashlets and move with bar to change their size. You can change:

change-size

Next steps