What does the Select and Load inputs of a RAM do (in Logisim)?
They are the equivalent to CS# and OE#

On RAM you have 3 control lines, all normally active low:


CS - Chip Select - Drive this low to enable the chip's functions.
WR - Take the address/data combination and store it in the RAM
OE - Enable the output of the RAM so you can read the data at the address specified by the address bus.


You never use OE and WR at the same time, but you always use CS in combination with WR or OE.