Click the "Sign In" link in upper-right hand side of the page. Enter your IU network ID and passphrase if required for authentication. Since there is no public content on this site, you will not see any items listed until signing in.
Items in the MDPI Internal Content site can be browsed in the same manner as in Media Collections Online, via searchable facets on the left side of the page. You will only have read-only access to the items, and will only see items you have been authorized to view.