how to relate tables?

friends,

i have a report which calculates ECS, EXSED, exbed, CESS, etc...the data is taken from tables J_1IPART2, J_1IEXCHDR, J_1IEXCDTL..now, i need to retrieve the values from finance tables for these values alone..how to go about this? i believe the same values for all the abovementioned fields will be stored in finance tables...how to link these excise tables with bseg, bkpf or other tables and what should be the conditions? pl help...thanks all