Q.orange wax begonia
I have an orange wax begonia that I just planted in full sun. Had lots of rain in the morning and full sun in the afternoon. I noticed when I returned home at night that some of the leaves have white spots on them and the plant looks like it is dying. Please help! The plant is beautiful and I would love to save it. I have had the plant for about a month. First I had it in a pot in mostly shade with some sun. I decided to move it to the front of the house with full sun and repotted it into a larger pot.

It sounds like your wax begonia is afflicted with 'powdery mildew'. You can read about powdery mildew and courses of treatment at the following link:
https://www.gardeningknowhow.com/plant-problems/disease/powdery-mildew-homemade-and-organic-remedies.htm
For more information on the care of begonias, please visit the following link:
https://www.gardeningknowhow.com/ornamental/flowers/begonia/annual-begonia-care.htm