If you really have Corsair LL120 fans they each have two FOUR-pin cables. One has a standard 4-pin fan connector about 3/8" (10 mm) wide with four holes two ridges down one side. This plugs into a mobo 4-pin SYS_FAN header and provides power and control of the FAN motor. The other also has four holes but a latching tab on one side, and should also have a label on the cord saying it plugs into the RGB Hub. This provides power and control of the RGB lights in the fan frame.
The RGB lighting system in these fans is of the more advance Addressable RGB type (aka ADDR RGB or ARGB). (The simpler type are called just plain RGB.) However, Corsair uses on their RGB equipment different connectors from what have become commonly used by many others, so connecting them to a mobo RGB header is a bit tricky unless you can get an adapter cable. And, of course, you can only do that it your mobo has a ARGB header on it.
The RGB lighting units in the fans need a source of power and something that can control the lighting display patterns. This is an RGB Controller, whether it is a separate box or a mobo header. Corsair designed their stuff for use with mobos that do not have the required mobo header, so they sell their own RGB controller and electrical systems. For example, the common way to buy the LL120 fans is in a 3-pack that includes a Corsair Lighting Node Pro (controller) and their LED Hub. There is a cable that connects an output of the Lighting Node Pro to the Hub, and then you can plug into that Hub up to six Corsair units with the non-standard Corsair RGB connectors. Each of these boxes plugs into a SATA power output from the PSU for power. To accomplish control of the displays, those items come with a cable to connect the Lighting Node Pro to a mobo USB2 header for communication. Then you download a free utility called iCue and install it on your system, and that utility is how you control the lights.
Without the Lighting Node Pro and the associated LED Hub, you would need to have the correct type of RGB header on your mobo. It MUST be of the ADDR RGB type (with 3 pins). Then you would have to find an adapter to connect your two fans' RGB cables to the mobo ARGB header. Alternatively, you might need to get the Hub without the Lighting Node Pro to connect both fans to, and then a special cable to connect the Hub's input port to the mobo header. OR, get both the Hub and the Lighting Node Pro. If you have the ADDR RGB header on your mobo, ask Corsair Tech Support if they can supply adapter cables of some type.