Using the Project Explorer there are several ways to open an editor.
In one of the navigation views select the file JanesFile.txt
To open an editor on the file choose one of the following approaches:
To edit a resource using the default editor for that resource, either double click on the resource (in one of the navigation views), or select the resource and choose Open from its popup menu.;
To use a specific editor to edit the resource, start by selecting the resource in one of the navigation views, and choose the Open With option from the popup menu.
The Workbench remembers the last editor that was used for editing a specific file. This makes it easier to use the same editor down the road.
The default editors can be configured using the General > Editors > File Associations preference page.