When importing images, you should apply color transforms to convert them to a connection space and then to your chosen working space. Different types of images require different transforms.
For example, suppose that you want to work with scene-linear values using the ProPhoto primaries. First convert the inputs to ACES, then apply ACES_to_CIE-XYZ followed by CIE-XYZ_to_ProPhoto-RIMM from the primaries/ directory. If desired, you can export a custom .ctf file that applies all three transforms in order.
On the other hand, if you want to import raw digital cinema camera footage and work with it using video-encoded values, you can import the images using the appropriate transform from the camera/ directory and then apply one of the transforms in the RRT+ODT/ directory.
If you need to convert Digital Cinema Distribution Master (DCDM) values to HD video, you can apply DCI_to_CIE-XYZ from the display/DCDM/ directory followed by CIE-XYZ_to_HD-video from the display/broadcast/ directory assuming that the DCDM was mastered to the DCI calibration white point. However if this results in unequal RGB values for colors that are supposed to be neutral, then you may need to replace the first transform with one that is relative to a different white point, such as DCI-D65_to_CIE-XYZ (see White Point Conversion).