To create a bar increase purlwise you will Insert the right needle into the stitch on the left needle from back to front and purl it.
Leave the new purled stitch on the left needle.
Purl again into the back if rhe stitch by twisting the stitch and inserting the needle through the back of the stitch and purling it.
Slip both new stitches onto the right needle.
After completing the nect row you will see the bar created by the increase.