In this tutorial: Editing Data Creating New Shapefiles Editing Shapefiles Snapping Modifying Polygons In the previous tutorials you have learned how to change the display of data and combine data sets to isolate specific categories of information. In this tutorial you will learn how to modify the data in existing shapefiles or tables, add data to existing files, and create new files of data. Editing Data For this exercise you can work with an existing data set (i.e. the wetlands data from the DC GIS site) or you can create an entirely new shapefile that will contain only your new data. If you choose to work with an exisiting dataset, skip the next section and go directly to Editing Shapefiles. Creating New Shapefiles In the first exercise you learned to create a new polygon shapefile. In ArcMap you added a box or circle to the shapefile and then used this polygon to clip larger data sets to the boundaries of your study site. You can use the same process to create a new shapefile that will contain any information you choose to put into it. For example, you might want to create a new layer, or shapefile, that includes additional habitat areas along the Anacostia so you can explore how the introduction of habitat areas might impact different components of the urban fabric such as systems of infrastructure, circulation, recreational areas and/or other habitat areas. Editing Shapefiles Whether you are working with an exisiting shapefile (wetlands) or the new file you just created (habitat_new) the process of editing and adding data to the file is the same. Source.