Fn Lock with no function key or BIOS option?

I have an Acer Aspire v15 nitro black. I love it, except I can't figure out how to lock the fn key, i.e. set the media key functions as the default operation of the function keys. I looked in the manual, there's no listing for function lock. I've been through all the settings, no luck. I looked at the bios, no options for fn lock. Anyone got any ideas?