Background Image secondary view of different axis

I’m trying to follow this tutorial here:

But I can’t figure out how to get the secondary view to display the background image on a different axis.

My main window is setup for Y (up down) X (left right) I need to secondary view to be Y (up down) z (left right) [I think?] How would I go about doing this?

Set up two background images and for each set the view you want to see it (Top / Front / Right etc). Then set each viewport to that correct view using the numpad keys/ Ensure each view is also in the orthographic view (toggle between perspective and orthographic views)

Unless you are using an ancient version of blender forget that tutorial and use one of the million tutorials that are used with a version of blender made within the last 5 years.