How speed of light helps us in time travel?
In standard concepts of Spacetime there is a speed limit which a wave or a physical object can attain.
It is the speed of light.
Going near speeds of light would slow down time just enough that you don't exceed that speed.
Since time is slowed down so is your aging process and there's an extra bit i.e. time elsewhere in the universe will run its usual way. By exploiting laws of physics in this way one cannot time travel but in a way fast forward the time.
But this method of time travel has its own consequences which is you can't revert back to time you started.