Creating anatomical ROI using aal atlas

Hi,
I want to create anatomical masks for orbital frontal cortex based on aal atlas and use that mask as the input in fsl. http://www.gin.cnrs.fr/en/tools/aal/ I downloaded the New version of orbital frontal cortex parcelation, on that website but when I opened the nii. file using fsleyes, they are just brain segmentations.
I have never used spm and I wonder how to get the mask for only OFC (including lateral ofc and medial ofc).
Please let me know if you know the answer and I appreciate your help.

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