Connectivity between SAP NetWeaver Portal & ECC R/3 system

Hi,

I need to establish the connectivity between the Portal & backend system.

Kindly provide me the step by step process or sequence of activities to perform to establish the connection between Portal & R/3.

ECC or R/3 system :     EHP6 FOR SAP ERP 6.0

Portal                     :     SAP NetWeaver 7.3 Enhancement pack 1 (newly installed).

Regards,

N S