Try using the one of the tools I mentioned earlier to configure your listener. Then try starting your listener.

BTW, when you did a custom install, didn't the assistant open the NET8 configuration? It might be a case you might have cancelled it. Don't worry, go ahead and use one of the earlier mentioned tools and configure your listener and then start is as folks mentioned and then try connecting to your instance that you had created. Make sure that the service entry is present in the tnsnames.ora file.

Good luck,
Sam