You mix working solutions straight from concentrates with color chemicals.
It is plain as day on the Kodak chemicals. If anything says "...to make XXX volume of working solution", just "to make...", or something similar, that means to use it straight. If the box says "to make", there you have it.
However, I have never read the Arista directions, so I do not know what they say. I would not be surprised if they were very bad.
The moral of the story? Buy Kodak chemicals when doing a Kodak process, for many reasons, including cost, separate bleach and fix steps, apparently for the better mixing instructions, and so on and so forth.