In the DX6i, you will click your wheel/roller (push the top of the roller only, pushing the bottom will break the roller) and scroll down to the Gyro menu. In there, it is probably set to "INH". You will want to change that to select a switch (I can't remember what switches or options you have, just don't put it on F-Mode). In there, you will want to put your gyro setting to about +65 to +70. On the DX6i, 50 is neutral. Anything below 50 is Rate Mode, and anything above 50 is Heading Hold mode. You always want to fly in HH mode.