ATC and Loki

Look at  Fletcher-Munson.  
Adjust by ear.
I presume that is why you're getting it.

Congratulations. I bet this is exciting. First, you want to listen to your new speakers. If you are interested in good sound avoid any equalization. Start by setting up your system and making sure all components are fully broken in… 200 hours of music play.

Typically speakers and listening position is an equilateral triangle to start with. You want the speakers away from the back and sidewall. The amount of toe in is really important. You might Google toe-in for your speakers, but start with them pointed at you and incrementally move towards alignment perp to wall. There is a best angle such that the sound stage is open and central image is solid and stationary. After set up you want to know the sound and then you can work on specific problems.

You want to take time. You spent a lot of money… the difference between a well set up system and one that is not is huge!

Then you can adjust the room. A rug in the right place, wall hanging, or even acoustic panel can completely change the room. There are key points for reflections that you may be able to dampen. I am guessing you have a glass wall behind? On wood floors, boxy room. These can best be dealt with by adjusting room acoustics.

The basic tenant of good audio is to never fiddle with the signal… so, no tone controls, no extra switches or adjustments as they all introduce noice and fowl up the signal.
Hope this helps.

Ideally you will connect the Loki between your preamps outputs and your power amps inputs. This is fairly simple if you have separates. If you have an integrated, you will need to use the pre outs and ins if your amp has them, otherwise you will have to connect it between the source and amp. After connection you just adjust each knob until you reach your desired sound profile.

The Loki appears to be a very wide band, very low "Q" tone control comprised of four filters, that per the diagram on the units front face plate appear to be shelving style filters. IOW each knob is going to cover a very large range of frequencies.