It is not possible from a app to place a widget in the home screen. Only the home screen can add app widgets to the home screen.
similar links link1, link2, link3
But you can offer user to pick widget from widgetpicker.
Intent pickIntent = new Intent(AppWidgetManager.ACTION_APPWIDGET_PICK);
pickIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, AppWidgetID);
startActivityForResult(pickIntent, KEY_CODE);
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