Complex sentence: On September 7,1918, the presidium renamed PTA and the Press bureau into the Russian Telegraph Agency (ROSTA), which became "the central information agency of the whole Russian Socialist Federative Soviet Republic".
Split into simpler sentences: On September 7,1918, the government presidium resolved to rename PTA and the Press bureau into the Russian Telegraph Agency (ROSTA). ROSTA became "the central information agency of the whole Russian Socialist Federative Soviet Republic".