Add an additional sidebar

On my secondary pages I have used the "right sidebar" template. I would like to have different sidebar "sections/boxes" for different items (I have already customized the sidebar in a child theme to have a border and shading so it is an actual box). This is what I am looking to do - Example: "Join mailing list" in top sidebar box Some other info in second box Contact me info in third box etc. How can I make additional sidebar sections? Thank you in advance!