how to reverse from one side of dress to the other
In general, to reverse from right side to left side, you could work decreases or increases at the end of a RS row (right front), at the beginning of a RS row (left front).
Increases or decreases at the beginning of the RS row for the right front could be worked at the end of the RS row for the left front.
This is the right front or left front as you would wear the dress. The above is one way of reversing the shaping but there are other ways.
Which pattern are you making?