What is the Syntax for Secondary Index in Program before Select Statement?

I am not sure what you mean to say about syntax of secondary index. there is no special syntax for primary index and secondary index in select statements, but if you want you can specify to use a particualr index always while selecting by using oracle % hint in the select statement follow the below syntax.

SELECT MAX( kkop~augbd )
INTO it_gen_docs-augbd
FROM ( fkkvkp AS vkp INNER JOIN dfkkop AS kkop
ON vkpvkont = kkopvkont ) INNER JOIN dfkkko AS kkko
ON kkopaugbl = kkkoopbel
WHERE vkp~exvko = ti_cuentas-exvko
AND kkop~bukrs = p_bukrs
AND kkop~blart IN r_blart
AND kkop~augst = '9'
AND kkko~blart IN r_blartd
%_HINTS ORACLE 'INDEX("DFKKOP" "DFKKOP~Z07")'.
DFKKOP is the table name and DFKKOP~Z07 is the index.