[Q] How to make a ROM support external sdcard?

[KuroKeita]

Currently, i'm having a HTC One J (the Japan variant of HTC One M7), all the hardwares are the same as M7's, the only difference is that my phone have sdcard slot and it use different partitions. The point is, i tried to port roms from M7 section so that it can work on my phone and it worked, but then the rom didn't support external sdcard, in the setting/storage, it only display Phone storage and USB storage. Can anyone have me as how to get the rom to support and recognize the external sdcard?