Constant Current and Constant voltage
In case you haven't noticed:


Voltage-limiting on = constant voltage
Current-limiting on = constant current


Both functions are always ever-present and will kick in whenever needed. The one whose limit is hit first based on the load that is connected will be the one to kick in. That means one of them is ALWAYS on.

For example, suppose you connect a load and set a voltage and current.

If the voltage limit will kicks in, then current that would drawn by the load at the set voltage is below the configured current limit. This results in a constant voltage supply.

If the load would draw more current than the configured current at the configured voltage, then the current limit kicks in. This results in a constant current supply.

Convenient, no?

EDIT:

The voltage and current displays on the supply probably only display the actual values of voltage and current the supply is providing. If you want to see the "set" value for the voltage or current limit thresholds, you have to work around this.

The current limiting works by reducing the voltage to a point where the current drawn by the load is equal to the constant current limit. That means if you make sure current limiting isn't on, then the actual output voltage is equal to the voltage limit threshold.

That means in order to read the voltage limit threshold off the display, you have to make sure current limiting is not active. The easiest way to do this is to disconnect the load. You may have to turn the current knob a bit past zero since some supplies interpret a current knob turned all the way down as "off" and will kill the supply voltage even if no current is being drawn.

Similarly, to see the current limit, you just have to connect a load and turn up the voltage until the output voltage stops increasing. That means the current drawn by the load at the attempted output voltage exceeds the current limit threshold. The output voltage is not allowed to increase because current limiting has kicked in. At that point, the actual output current on the display is equal to the current limit threshold.

Obviously, that means always start your BOTH knobs LOW and alternately turn up each one a bit so that they  slowly more or less together until you have a good idea of what you are able to get away with for your load. Never start high or you can damage something.