Debugging with Custom GDB Server
It is expected here that you have already built your application and created a debug configuration for it. About how to do it you can read on the following pages:
Specifying custom GDB server properties
You can use some other GDB server. In that case you should specify a path to this server executable file, its command-line arguments and also commands to be passed to the GDB client. These are on the Commands tab of the dialog.
OpenOCD as a custom GDB server
To use OpenOCD as a custom GDB server, user needs to specify command line options for OpenOCD. It is not necessary to specify any commands for GDB on the Commands tab, it will connect to OpenOCD automatically.