Once you are up and running, just click File-->Open and choose the text data file to open (.csv for Gtech data)
Sometimes the map may look a bit off. This is unavoidable when dealing with surfaces that are not perfectly flat or when the car over or understeers a lot. In that case you will need to go through the following steps to prepare and correct the run:
Trim the run: Autocross runs will have some stationary time before the run. Since no surface is perfectly level, the hardware will still think you are slowly moving. Using the top, large slider, move the yellow indicator dot to the start of the run. Once there, click the CB button to cut away everything before that point. Now move the slider to the end of the run and use the CA button to clip away everything after that.
Set the initial velocity: For autocross runs this is typically zero, the default. Otherwise, set it yourself in the initV field.
Calibrate the run Using the smaller sliders on the side, you can calibrate the run. It will only change the correction factors for points AFTER where the run slider is currently set. I reccomend moving the large run slider to the start of the run, then use the calibration sliders until the track looks close to correct. You can then move the run slider forward to correct later areas of the track as needed.
Once the track looks good, you can then feel free to use the run slider to analyze your run. You may also find the friction circle at the top left helpful. A magenta dot appears on it as well to correspond with your position on the map. Red means braking, green means acceleration, and blue means 'coasting'. You will also find sustained and instantaneous G information for the run on the right.