The object code must be loaded into the Erlang runtime system. This is handled by the code server, see the code(3) manual page in Kernel.
The code server loads code according to a code loading strategy, which is either interactive (default) or embedded. In interactive mode, code is searched for in a code path and loaded when first referenced. In embedded mode, code is loaded at start-up according to a boot script. This is described in System Principles.