Your confused because you (and everyone else for that matter)
are unable to perceive time in the same manner as you perceive the three spatial dimensions. As far as actual time travel, it can not be explained simply.
The most straight forward type of time travel would be the result of relativistic time dialation. This is a consequence of the special theory of relativety. With this form of time travel, you would point your machine in any direction and physically move very fast, near the speed of light. When you return to your point of departure you will be many years in the future. How far in the future, well that depends on exactly how fast you were traveling, and for how long.
if i have a time travel machine i can only tell it to go "when" and not "where".this will create a lot of confusion.please explain me in simple terms.