For the NIRSpec MOS session, download this file. It will unpack as 2020_steward/MOS and contains 2 catalogues plus a trial APT file. And this file for the ETC part.
For the IFU session, download this file. It will unpack as MIRI_IFU_example and contains a pdf on the MIRI MRS ETC and APT example, and a spectrum that is required for the ETC example.