By default, Plot writes y labels only to a single y-axis, typically shown to the left.
To create an axis on the right, use option y2axis.
Label options or data given before option y2axis, are applied to the left y-axis, and label options and data given after are applied to the right y-axis. The x scaling is the same for both.
For example:
dat=. i:2j30 pd 'reset' pd (;sin) dat pd 'y2axis' pd (;^) dat pd 'show'