What is energy? “Energy” (or psi) is a word we use to mean the stuff that makes psionics work. The term “energy” is pseudo-scientific at best. A lot of us don't actually think we're talking about the energy as discussed in your physics class. We just use the words “psi” and “energy” to tell each other about our experiences in a common language.
Much like mathematics has been created as a framework for understanding and using physical processes as a tool, we use the understanding we do have in psi(the "stuff" that makes psionics work) to formulate frameworks to sufficiently help explain phenomena we do not yet fully understand ( we do not yet formally understand how Psionics works). These symbolic frameworks are useful in understanding how to do psi, and understanding the way in which we have observed it working. Thus, when we say things like "energy", most of us agree that we aren't actually talking about "energy" in the physical sense(i.e. kinetic, potential, spring, etc). What is energy? Energy is just a word we use to describe a mechanism for a process that occurs psychically.
About Applying “Energy”
You can apply “energy” using thought, action, or both. Traditionally in the psionics community, people use thought, but you definitely don't have to.