If you have a dataset directory, you could use os environment variable named YOLOX_DATADIR. Under this directory, YOLOX will look for datasets in the structure described below, if needed.

$YOLOX_DATADIR/
  COCO/

You can set the location for builtin datasets by

export YOLOX_DATADIR=/path/to/your/datasets

If YOLOX_DATADIR is not set, the default value of dataset directory is ./datasets relative to your current working directory.

COCO/
  annotations/
    instances_{train,val}2017.json
  {train,val}2017/
    # image files that are mentioned in the corresponding json

You can use the 2014 version of the dataset as well.