This works on my fx-9860G (which i believe is very similar):
Start with pressing the OPTN button. Then press F6 to get to the next page. Press F3 (PROB) to find Ran# (on F4) or F4 (NUM) to find Int (on F2). To summarize:
Int: OPTN, F6, F4 (NUM), F2 (Int).
Ran#: OPTN, F6, F3 (PROB), F4 (Ran#).