To set emulator command line options for a MIDP project, type in the command line switches. See Running the Emulator From the Command Line.
For CLDC projects, the Regular execution button is enabled by default. This means the setting for “Specify the Security Domain“ applies when the project is run on an emulator. It does not apply for OTA provisioning or an external emulator platform.
If you do not check Specify the Security Domain the project runs with the default that was assigned when the project was created. If you check the box, you can select a domain from the dropdown list. See Security Domains and Specifying the Security Domain for a Project.