To add a new custom widget, you need to go through 3 basic steps. Open your dashboard, click on the Edit Mode button on the left:

Then, in the right sidebar click on “Add Data Widget”. After that, choose a specific Integration, for example, Google Analytics, select Account, and click on the blue NEXT button.
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The next step is to choose the Property and the Profile (view) of the website, and then to select Custom from the Widget dropdown menu.

Select Segment, Dimension and Metrics to get all the data for your widget.

You can select multiple Metrics, which is great for the Table widgets. You can also add Calculated metrics. Generally, a custom widget works the same way as Custom Reports in Google Analytics.