The video you linked to basically tells you everything you need to do. I don't believe the process has changed for end-users in a long time. Key thing is to make sure you use the GBA BIOS and enable the JoyBus connection.
I'm not sure the JoyBus option is enabled by default on OS X builds of VBA-M. That's probably why you might be running into a wall. The JoyBus option is definitely available in the Windows version though.
I'm not sure the JoyBus option is enabled by default on OS X builds of VBA-M. That's probably why you might be running into a wall. The JoyBus option is definitely available in the Windows version though.