That^^^
If, like int he simiplified and application schematics in the datasheet, there isn't a voltage divider on the Vout, then you'd have to install one, cutting the trace from Vout to the actual voltage output of the system. Install the (5kohm to 10kohm, probably) potentiometer with one outer pin to the actual votlage output, the other to ground. The center pin (wiper) goes to the Vout pin. Before turning it on, set the pot to max, meaning turned all the way toward the actual voltage output connection end. Then very slowly adjust it towards teh ground end until the voltage output reads what you want it to.