this is simple to do,
make a while loop with 1==1 for the condition to make it run forever
use an rxinput command and store it any variable (use the help menu for this)
then use an if command to check the value of the variable you used previously
then drag in the motor blocks
then do another if command for the opposite direction
and drag in the motor blocks
look in the help section for more info (in easyC)