Hi,
Have you tried reading the doco on the BAPI itself?
After that, I would do a where-used to see how to use it.
I admit, there are a lot of parameters, but you can successfully post document with relatively few of them:
* post the GL document
CALL FUNCTION 'BAPI_ACC_DOCUMENT_POST'
EXPORTING
documentheader = ls_documentheader
TABLES
accountgl = lt_accountgl
currencyamount = lt_currency
return = lt_return.
cheers
Paul