Technical support in FSL.

I started to use the FSL (FMRIB software library) to analyze brain images.
I have a basic trouble to be unable to convert DICOM files to a NIFTI file (.nii.gz) by using the dcm2niigui dawnloaded from a mricron Website ( I use Mac OS X.6.6 to operate these software.
Does Somebody know the trouble touting in this situation. Otherwise, Please tell me the other way to convert DICOMs to NIFTI using a Shell command line.