Hello @Elijah-web ,
With the Sketch widget, the graphics you draw will exist on a GraphicsLayer. If you are having issues seeing the graphics you draw, it is most likely a spatial reference difference between the graphicsLayer and the view's spatial reference.
You can of course implement your own code to call FeatureLayer.applyEdits() and pass in the graphics you sketch with the Sketch widget to add the graphics to the FeatureLayer (keeping in mind that the graphics drawn and FeatureLayer must have the same spatialReference). However, it will be easier if you just utilize the Editor widget in your app. The Editor widget uses the same SketchViewModel that the Sketch widget uses. This means users of your application will be able to draw features and save them to the FeatureLayer. You don't have to add any additional code to save the changes to the layer, since the widget takes care of it.
Here are some helpful links to get you started with the Editor widget:
1. Api-reference documentation
2. Tutorial
3. 2D Editor Sample
4. 3D Editor Sample