There are several ways to accomplish your goal.
Here is what I would try first. Connect the SM802MS to the Scarlett 2i2 audio interface using a 1/4 inch male TRS to Dual Male RCA Cable like the one pictured here:
Connect the RCA pins to the RCA output jacks on the top right of your mixer. Be sure to use the output vs. the input. Plug the TRS plug into either one of the Neutrik Combo Insert Sockets on the Scarlett 2i2. Set the LINE/INST switch next to the socket to LINE to tell the 2i2 that you are using a TRS balanced plug vs. a standard TS instrument cable.
After you have connected the mixer to the interface, set your gain control on the 2i2 to prevent clipping. Now you should be all set to record the signal from your mixer into your DAW on the computer you connect via USB to the 2i2 interface.
Another option would be to use the headphone out on the mixer to connect to the 2i2 interface using a TRS male to TRS male connector. Everything related to the 2i2 interface is the same. The only difference is how you connect the other end of the cable to the mixer. Be sure to set the headphone volume at no more than half way.
The third option - if you aren't using your control room out sockets on the mixer for sending the signal to stage monitors or a control room, is to use a cable like the one pictured below to connect to your interface via the control room out sockets:
EDIT: It is not common to attempt to create a stereo image in a live mix since only the audience sitting between the two mains stacks or speakers would benefit and the audience to the left and right of center would miss part of the sound on stage. But if you are using stereo effects in your live mix and you want to capture those effects in your recording, you could use a Dual Male RCA Cable to Dual Male 1/4 inch TS cable (pictured below) and plug one 1/4 inch TS plug into each of the two input sockets on the interface.
