Licensed users have the option of launching with files that are created using the extension OR existing data files that are selected as shown in this topic.
If you have existing EVS geology or chemistry files (or wish to use any of those supplied by C Tech) you can select any of the EVS file types by clicking on the View EVS Data button in the ArcMap window. When you do so, the following window will appear. Note: if you created a chemistry file (as in the previous topic) you will already have a chemistry file specified
For each option there is a button named "Load existing file-type
file" (e.g. "Load Existing CSV File"). The discussion of
EVS file formats can be viewed by clicking here: 
Geology & Chemistry File Formats
To demonstrate let’s Load a geology file and chemistry file, thus enabling all of the EVS for ArcGIS applications.
First, choose the following CSV file (in the ctech\data\chemistry folder) by selecting the Load Existing .CSV File button:
Then choose a geology file so we will have application choices that include both chemistry and geology applications. For this example we will choose a .geo file (though the applications will use either GMF or GEO files. Please note that .gmf files are selected with the Load Existing .GMF File button. Pick the following .geo file (in the ctech\data\geology folder) by selecting the Load Existing .GEO File button:
Once this is done, the "Current EVS Data Files:" window should list both files as selected as shown below:
What have you accomplished by selecting both a chemistry file and a geology file?
By making or choosing both data types, the ArcGIS extension will now make available nearly all the applications provided with EVS for ArcGIS (or whatever version of C Tech software you are working with). Once you choose Launch Application from the EVS pull-down you'll see there are applications for viewing chemistry mapped into geologic layers, posting chemistry data, rendering geologic layers, and much more. If you had only chosen a CSV file, you would only be shown the group of applications that only require chemistry data. Similarly, if you had chosen only a geology file (GMF or GEO) you would only have geology applications available.