How to make a popup appear on the side/bottom of the page instead of the center?
The Popup on Load module leverages the Colorbox module, and its jQuery plugin dependency, to style the pop up. The module allows for your own custom style which will let you adjust the popup position to where you want it. This is covered in its documentation.


  Add a custom Colorbox style to your theme
  
  The easiest way is to start with either the default style or one of
  the example styles included in the Colorbox JS library download.
  Simply copy the entire style folder to your theme and rename it to
  something logical like "mycolorbox". Inside that folder are both a
  .css and .js file, rename both of those as well to match your folder
  name: i.e. "colorbox_mycolorbox.css" and "colorbox_mycolorbox.js"
  
  Add entries in your theme's .info file for the Colorbox CSS/JS files:

stylesheets[all][] = mycolorbox/colorbox_mycolorbox.css 
scripts[] = mycolorbox/colorbox_mycolorbox.js

  
  Go to "Configuration" » "Media" »
  "Colorbox" and select "None" under "Styles and Options". This will
  leave the styling of Colorbox up to your theme. Make any CSS
  adjustments to your "colorbox_mycolorbox.css" file.