How can I set a flag to Nethersx so I can use CHD files?

I'm using a Retroid Flip 2, don't think that matters as it's Android, but I'm trying to play some games for Retroachievements and the games are in .chd format. I saw that you can add a flag to get the emulator to detect them but how do I do this? I don't have access to my PC right now but I've been poking around the files in Android and googling and found nothing that made sense to me, and I'm not sure if I can convert the files but if I did I'm sure it would affect the earning of achievements so don't want to go that route.

Anyone have any advice? Thank you!!