In a terminal window, go to your output directory, go into the PythonScripts directory and type
python3 tissue_seg.py

Otherwise, in your output directory delete the 'ABC_Segmentation' directory and launch Auto_EACSF again. 

It will run start the execution and run the tissue_seg.py script for you. 

The tissue segmentation should use the skull stripped image, perform a registration with the adult atlas template and run the EMS algorithm.