To run autonomous code, you simply need a Micro-USB port to USB-A port cable which you can connect from your brain to your computer. No controllers are required in the process.
As you have no controller, the program is effectively always running code as autonomous. If the code is using a competition template, just call your “autonomous” function at the beginning of main (or move it under a when started block if you are using blocks). You will obviously need to start the program from the V5 brain. Running this way does seem a little inconvenient, do you plan on having a controller at some point ?