Complex sentence: Internal circulars and documents explaining the church's guidelines, considered as having the same authority as the Biblical epistles as they come from the Chief Apostle, are supposed to provide the correct meaning of Bible and are not available to ordinary members, but only to elders.
Split into simpler sentences: Internal circulars and documents explaining the church's guidelines, which come from the Chief Apostle and are considered to have the same authority as the Biblical epistles, are supposed to provide the correct meaning of Bible. They are not available to ordinary members, but only to elders.