Jason here from Shopify Support.
Great question! Keep in mind that Pop is a sectioned theme. Here's a great guide on how to add a sizing chart on your product page.
For the shipping page link, could you let me know what you have in mind, please? If it's a hyperlink you're looking for, you can do so by Shopify admin > Products > Product description > Rich text editor.
Just in case if you need a detailed step by step breakdown, here's how to insert links with the rich text editor.
If you run into any issues, or if I misunderstood what you're hoping to set up, feel free to reply back here and I'd be happy to help out!
All the best,