I have successfully assembled the balloon, inflated it, and boarded it. I can get it to move around with the arrow keys and change the direction using the fan we found in a dungeon to change the wind direction. However, I cannot figure out how to make it ascend up into the air. Thus, it will not get me over the mountains to reach the temple of Singularity. What is the proper command to make it ascend?

After some more exploring I found that I didn't have to make the balloon ascend more because I found a pass through the mountains that the balloon was high enough to fly over. The temple has been reached.