The "edit" view of the dashboard allows you to adjust the size of each insight as square tiles. See screenshot below, with a red arrow where you can use the mouse:
Once you are done with the "edit" screen you can view results in the "view" screen.
If your question is relative to the overall size of the dashboard, we use a responsive framework to adapt the dashboard size to the actual size of your browser window. Note that display may not be optimal on small windows and computer screens with low resolution. Playing with the browser zoom factor may help in some cases.