Can someone please explain how the sun produces nuclear energy?

the sun is constantly releasing helium and hydrogen...
its an awesome process called nuclear fusion

Now, I'm no solar scientist, but, what appears to happen is this. The heat and pressure inside the sun means that the hydrogen atoms are constantly moving around at enormous velocities. Sometimes, 4 hydrogen atoms will crash into each other with such force that they sort of stick together to form a helium atom. Now, here's the clever bit. The mass of one helium atom is a tiny bit smaller than 4 hydrogen atoms.The difference in mass is converted directly into energy via Einstein's famous equation E = MC^2.That is the energy we see and feel as heat and light here on earth. The process is called nuclear fusion, since the hydrogen atoms stick or fuse together.

The weight pressure inside the star is so great that, despite their electrostatic repulsion, even protons are squeezed close enough for them to merge and form a Helium nucleus. So this is the nuclear fusion of hydrogen, and it release a lot of energy. If a star collapses further, other fusion processes produce heavier elements. Finally, when the star explodes, these elements are thrown in space and sometimes form planets. Yes, we are all stardust!!

most of the sun mass is composed of hydrogen and its atmosphere has a lot of  it.. as the temperature on sun very very high...so at this high temperature every four hydrogen atoms fuses  to form one helium nuclei.the this formation of nuclei is the source of nuclear energy . during this reaction of nuclei formation a lot of  heat energy is also released , apart of this heat and light is came to earth. the reaction of helium nuclei formation is called fusion reaction.