How do you figure out how much energy a certain frequency of light has?

Energy = Planck's Constant x Frequency
Joules = Joule.Seconds x 1/seconds

Planck's Constant (h) = 6.626x10-34J.s

E=hf is the equation for the energy of a single photon with frequency f (h is Planck's constant).

Saith: what these people are giving u is the energy for a single photon. U ask for the energy of light in general but to get that u would also have to know the amplitude of the light you are emitting (amount of photons or intensity of light).

What do you mean exactly by "energy", is that electron volts rather than joules? Does the frequency have to be its frequency in MHz instead of GHz or THz for that equation to work?

Put your frequency in Hz. If you use 6.626*10^-34 as Planck's Constant (h), you will get an answer in joules.

I get the 6.626*10 part, it's 66.26 billion. But what is the ^-34 for?

The "'^" symbol means "to the power of". You take 6.626 times 10 to the power of -34. It would be the same as 6.626 * (1/10000000000000000000000000000000000). That's 34 zeros. As you can see, this results in a very small number. There isn't much energy in an individual photon.

I get the 6.626*10 part, it's 66.26 billion. But what is the ^-34 for?

Perhaps written in the following form is more informative.

h = 6.626 x 10^-34 J s.

i.e.

h = 0.000 000 000 000 000 000 000 000 000 000 000 6626 Joule.second

Note: 1 Joule.second = 1 Joule per Hertz
So, when you multiply h by the frequency in Hertz you get an answer in Joules.