Locate the Clear CMOS jumper (usually labelled CLR_CMOS or similar).
The official manual is no longer hosted on MSI’s global front page due to the board’s age, but it is still available through legacy support channels and third-party archives. ms-7613 ver 1.1 motherboard manual
This board is notoriously picky with high-density DDR3 RAM. It generally prefers "double-sided" modules (chips on both sides of the stick). Locate the Clear CMOS jumper (usually labelled CLR_CMOS