You can access the EHRI resources here:
EHRI Portal gives online access to dispersed Holocaust sources
EHRI Research Guides on Terezín and "Jewish councils"
Since June 2017, EHRI also hosts IRP2 the International Research Portal for Records Related to Nazi-era Cultural Property
Please, also click on these links for more information.
Or for the EHRI Portal, wacht this video that gives a short introduction. You can also find it in the Portal Manual.