I've not used this particular board, but some RS485 modules that don't have /RE & DE have some sort of auto switching built in that switches the RS485 line driver from Rx to Tx and back again.
I had a quick look at the schematic for this one and I can't figure out how it switches into receive mode as it looks like both /RE and DE are pulled high all the time.
Looking at the connector on the left, you supply VCC & GND and your Tx + Rx serial data lines. If the code you have references RE & DE, then you could either comment that out or assign them to unused pins.