Problem with SQL 6.5 identity fields

I have problem with inserting records into two tables
in relation ONE to ONE. They are connected via int field (I_LINK).
In table where that field is primary key I defined it as
identity field.

Problem is that I can't post records into table where I_FIELD is
foreign key. I don't know how(where) to post first table, so that
identity field is filled by server and then to copy value that
was inserted to other table.

Please help, this is driving me nuts.