You open the Standard Web Project Properties dialog box by right-clicking any and choosing Properties.
The Sources page lets you define the folders that contain the project's source packages and test packages. Use the buttons on the right of the dialog box to add, remove, and change the order of the folders.
You can have multiple source roots in a standard project, with the following exceptions:
You can use the Source/Binary Format drop-down menu at the bottom of the Sources page to set the Java platform version that the generated Java code should be compatible with. This setting corresponds to the javac -source option.
Test Packages Folders
You can use this pane to specify the folder that the IDE uses when creating JUnit tests. By default, when you create a project the IDE creates a test packages folder called test with the label Test Packages. Use the buttons to the right of the list to remove the selected folder or to specify the folder that the IDE uses when creating tests. You can also modify the Label field to change how the folder is displayed in the Projects window.
To create JUnit tests with the IDE, a project must have a test packages folder. If the test packages folder for your project is missing or unavailable, you can create a new folder in your project and then use this pane to designate the new folder as the test packages folder.