You must configure an ENGINE_SECTION which looks like this:
pkcs11 = pkcs11_section
engine_id = pkcs11
dynamic_path = /usr/lib/engines/engine_pkcs11.so
MODULE_PATH = /usr/lib/opensc-pkcs11.so
init = 0
Please note that the key file which must be specified in the configuration
must be the idenitifier of the key on the smartcard an not a real filename.
A typical OpenSC example for a name is id_45.