Once you are logged in to your account click on the "Features" tab on the side bar.

Then click on "Polygons".

Under the "Update" column click on the green symbol of the polygon you want to edit.

Click on "Map".

Make edits to the polygon by clicking on one of the lines (the polygon will become blue) and dragging it. 

Click on the "save" symbol on the top right and then close the window out. 

Note that under the "Geo-spacial geometry" the map is now "Updated". Click on "Save".

The polygon has now been edited and saved onto the map.