I can't find the values of the currents
IO max is your maximum load current - how much current you need to run your load at the output voltage.  Calculate I(PK) using the equation you have circled and as @scorpdaddy says, if its less than 500 ma you are ok without the external transistor.  Otherwise add the transistor.

Choose Rcl to give you the current sense you need, and choose a transistor with a collector current in excess of your calculated I(pk).  Choose appropriate base resistor divider values low enough for sufficient base current.