Load your setup.json — every value is explained in plain English (tyre pressure in psi), and one click turns a twitchy setup into something you can drive. Everything stays in your browser.
Documents\\Assetto Corsa Competizione\\Setups\\[Car]\\[Track]\\ — that is where ACC stores your setups. Load the file of the setup that is giving you trouble.
On PlayStation and Xbox you cannot import setup files — you have to enter the values by hand in game. That is what setup viewers are for. The difference here: this one does not just display the numbers, it explains every single one in plain language, including the tyre pressure conversion to psi. You come away knowing not only what to type in, but why.
Then there is the second half. Pro setups from the internet often feel undriveable to beginners, so one click produces a calmer, more forgiving version. Only safe fields are toned down: more TC and ABS, more rear wing, brake bias forward, softer anti-roll bars, less differential preload. Springs, dampers and ride height are left untouched, because wrong values there make a car worse rather than better. Everything runs in your browser, nothing is uploaded.
On console you cannot import setup files. You open the .json in a setup viewer like this one and copy the values into your setup by hand in game. This viewer also explains what each value does, so you know what you are setting.
Under Documents\Assetto Corsa Competizione\Setups\[car]\[track]\. That is where ACC saves all your setups as .json files. If the folder for a car or track is missing, save any setup once in game and ACC will create it.
The setup.json stores a raw value, not a real unit. The approximate psi value comes out of 20.3 + raw value × 0.1. This tool converts that automatically.
Nothing is uploaded. The file is read and processed purely locally in your browser — there is no server that ever sees it.