Smooth & Edit from the Shape panel in the right sidebar. After this, the object will be now converted into a subdivision surface.
You can Extrude, Inset, or generate Edge Loops:
You can add Loop Cuts and use the Slide Tool to reposition the edges:
Also, you can modify and dissolve vertices (points), faces (polygons), or edges (lines):
Finally, you can fill holes by selecting the edges:
The following parameters can be adjusted under the settings menu:

