First, be sure that your Unity is up to date by following this guide
Connect your Unity
You should power the board on, open the app and click on "Scan" and "Connect Bluetooth"(mobile device)
click on the "Connect" tab in the UI and click "Connect USB" (PC or Mac)
The bottom of the screen will say "Connected to xxxxxx"
Whether you are on the Iphone, Android Mac or PC version of the UI, the screen should look the same or very similar.
You will need to find the 'config' top tab and the 'motor calibration' drop down menu.
Max motor current can be increased or decreased to allow for more or less acceleration. Remember, the higher that value, the less range and the more heat your motors will make!
Max brake current can be increased or decreased to allow for more or less braking power. If you are a heavier rider, you may want to increase that value, otherwise the stock setting is seems to work fine for all!