What? What line of logic did you use to come up with the necessity to "travel" among them just because they exist?
Reading on I see you've confused the many worlds model with the multiple universes model.
The many worlds model is the one where the mathematics of quantum physics can be used to show that each event in this world results in uncountable possible outcomes in the next instance. And those spawn more possible outcomes etc. etc. And, according to the many world models, you, I, and my dog Boots could exist concurrently (whatever that means across different time-space threads).
Note the word "concurrently." Our alter selves, our doppelgangers, are not traveling among the many world lines as they are replicating with each new line of events. Also note these many world lines are occurring in our local universe, not other local universes. Many worlds...not many universes.
This is of course a prime example where math shows something that has no basis in physics. But this is the many worlds model, not the multivariate model. There are in fact several of these.
Brian Greene in "The Elegant Universe" describes two that are memorable: the loaf of bread model and the big bubbles model. In the loaf of bread model, we have an uncountable number of slices of universe that, together, make up an infinite and eternal loaf of space time. Each slice of space in the loaf is separated by some space time that disallows us to see across the boundaries from loaf to loaf. And, the model say, when one loaf bumps into another loaf, that releases low entropy energy in both loaves that people in our local universe have called the big bang.
The bubbles model imagines a high entropy, infinite and eternal mother universe filled with huge and uncountable quanta. When one of these had an event mother universe laid a small egg of low entropy space time we call the big bang. As the mother universe is infinite and eternal, such quantum events are continually happening and new eggs are continually being laid...new local universes are popping into sime and space like so many soda pop bubbles. There are more out there but we can't see beyond the rim of our own local universe.
I recommend you read Brian Greene's book and then come back with a question if you still have one.