In order to set the radio to High Power you can do it one of two ways.

1. In the global Configuration go to Menu / Controls Tab, move the TX Power from the Main menu available box to the used box, make sure you have one of the programmable buttons is assigned Menu. If you write to the radio, when you select Menu, TX Power will now be a selection, if you press enter you should see HIGH and LOW in the display, move the arrow on the left up or down to select High or Low, then press enter, the radio is now set either in High or Low Power.

Another Method is

2. In the global configuration go to Menu/Controls tab, move the TX Power from the Main Menu available box to one of the programmable buttons Diamond, Up Arrow, Down Arrow, or Square. Write to the radio, in the display above the button you assigned TX Power you will see LPW which stands for Low Power, if it is highlighted the radio is in low power, if not highlighted the radio is in high power, you can toggle between low and high power by depressing the assigned key.