Shopify Page Resizing for Custom Content

I have a Shopify store and I'm planning to add some blank pages that will host custom content. I need help resizing these pages to ensure they fit well and display correctly.

Ideal Skills:
- Shopify development
- Web design
- CSS/HTML knowledge

Experience:
- Prior experience with Shopify
- Portfolio of Shopify stores or pages designed/resized.


Please provide me instruction as I am fairly technical.