All of the files, including images and catalogs, can be found at the DES file server: http://desdr-server.ncsa.illinois.edu/despublic/. All of the files are partitioned by tile. By querying the tables DR1_TILE_INFOand DR2_TILE_INFO, one can find the url for a specific file and tile. The columns on the catalog files are the same as the DB Tables.
As stated in the DES DR2 FAQs:
First need to read the DR2 release paper