First things first - Nikola Tesla was an engineer, not a physicist. In fact he flunked out of university (
Imperial-Royal Technical College in Graz) during his junior year in 1875 and never returned to complete his undergraduate degree. What education he had was strictly Newtonian-Maxwellian pre Einstein, Bohr and Heisenberg (Special Relativity, General Relativity and Quantum Mechanics). He was brilliant but he wasn't formally educated beyond what today would be an Associate of Science degree (Community College).
Second - your quote was close but not quite accurate. The quote should be, "If you want to find the secrets of the universe, think in terms of energy, frequency and vibration.”
That being done let's look at the three criteria. Vibration is a periodic oscillation of a rigid body and frequency is the interval per unit time between the passing of the peaks of the oscillations. In physics "energy" is defined as the capacity to do work. "Work" is defined as a force that can cause the movement or displacement of some object.
His three criteria are trivial. They don't say anything new nor do they impart much in the way of insight into the nature of reality. BTW: I've only seen third parties provide the Tesla quote, have never seen the direct quote from a Tesla document and I've never seen a third party quote with an attribution pointing to the original document for the quote. I don't know if it really is a Tesla quote or something made up for the internet.
Now to the question about frequency. So we have AM radio stations and PET scans. People are exposed to AM radio waves every day. They are in the very long wave spectrum. People go to hospitals and get PET scans every day. PET scans are in the ultra short wave spectrum shorter than X-rays and just a bit longer than gamma rays. None of the folks who are exposed to AM radio or PET scans disappear as time travelers. If you expose them to shorter waves than a PET scan then you first bombard them with gamma rays and if you go shorter its cosmic rays. The earth is constantly bombarded by both and it doesn't time travel. Expose actual people to them and they simply die of radiation poisoning. (We are alive because our atmosphere protects us from cosmic and gamma rays.)
So, can you time travel simply by ramping up the frequency of some energy source? No. You can time travel to the future by just going very fast. People in commercial airliners time travel to the future at an accelerated rate every time they fly (not much but it is measurable). An airline pilot working for 30 years could travel a millisecond into the future during a career. We have to constantly re-calibrate GPS satellites in orbit because they are traveling at ~19,000 mph and experience the effects of special relativistic time dilation which would cause their accuracy to degrade to uselessness if not for constant re-synchronization.
Time travel to the past has only been shown to be a theoretical possibility because there are thousands of possible solutions to general relativity that suggest the possibility if - and only if - you carefully choose criteria not known to exist in the real world as we currently know it. Kip Thorne's grad student came up with "exotic matter" as a solution for Carl Sagan as he wrote "Interstellar." Sagan, a brilliant scientist in his own right, asked Thorne to help him come up with a reasonably scientific solution for travel through a wormhole because wormholes, by definition, are unstable. The exotic matter would exhibit anti-gravity properties and would be used to line the wormhole interior and force the mouth to stay open and not pinch off. It worked for his novel but in real life? Exotic matter has never been found - its completely theoretical. It would take billions of tons of the stuff to line the wormhole. The wormhole is unstable with no exotic matter, so approaching the damned thing would likely cause it to pinch off before you could line it with the stuff.
And this is just the "short" answer.
