The process that powers the Sun is a nuclear reaction that occurs at the center where it is hottest: 15 million degrees is our best estimate. There the hydrogen atoms that make up the Sun are broken down into electrons and protons. The protons combine in a series of reactions to produce helium. The mass of a helium nucleus is less than the 4 protons needed to make it up, so the excess mass is converted to energy according to Einstein's equation E=mc2 where m is the excess mass and c is the speed of light. This energy gradually makes its way to the surface of the Sun and out into space.
The question is somewhat unclear. There is now on specific process of type of processes that is used for either generating or using solar energy. Solar energy is produces by the Sun, and is then radiated out by it all around in the form of light heat and other radiations. A minute percentage of this energy reaches the earth and provides it with heat, light and other form of energy. The light is received on the earth is used here as light. There is no special process involved. Similarly the heat energy of the sun is absorbed by the surface of the earth and various objects that exist on the earth, on which the sun rays fall. Such heating causes, among other things, the evaporation of water from water bodies, starting the cycle of formation of clouds, rain, and then collection of rain water in the water bodies.
One significant and special way in which the sunlight is used on earth is photosynthesis, in which plants absorb sunlight and use it for making their food from carbon-dioxide available to them from atmosphere.
Humans have applied some technological devices to utilize more of solar energy. These includes devices like construction of special panels that abosorb more of sulight and use it for purposes such as heating of water, use of photo-electric cells for generation of electric energy from solar power, and various ways of oncentrating solar radiations at one location to create hight temperature at such locations. These devices are then used a varied purposes including for cooking of meals in houses and for generating steam for various purposes ingluding power generation.