You will set the current for whatever the forward current of the LEDs is. You have shown 2 different specs, the first one indicated 1400mA and the second one 1050mA. That is what you want for the current. You set the voltage output to a little above the expected voltage, in this case, maybe 5V. The way a current limiter works is by setting the voltage to whatever is needed to draw the required current, but not to exceed the voltage setting.
Since the LEDs are in series, they all receive the same current, so you do not multiply the current by the number of LEDs.
Assuming you have a multimeter, here is how I would proceed.
1, With just the voltmeter connected to the output, adjust the voltage output to 5V.
2., Set the current limit to minimum. Verify it by connecting an ammeter in series with a resistor and LED, with the resistor being enough to limit the current well below the desired current, say 100Ω. The current should read near zero at the minimum setting, and go up as you turn it up.
3. Now connect your 3 LEDs in series and in series with the ammeter to the output, and adjust the current limit up until you reach the desired current (either 1400mA or 1050mA depending on which posting of the specs was the correct one.)
By the way, the stars the LED are mounted on are not enough for heat sinking. These are intended to be mounted to a larger heat sink. If you do not, they will get very hot and possibly the LEDs be ruined. That said, I have run up to about 600mA to 1W LED on one of these stars without damaging it.
Bob