Yes, you have full control over your theme customizations, so you just need to add links.
For example, if you want to link to Amazon:
<a href="https://amazon.com/the_rest_of_the_link" target="_blank">put text or image here, this will be the link</a>
So to add to your site you would do this:
1) Duplicate your live theme so you can work on a backup theme without affecting the live site.
2) Add the links in the code where you want them to show up. For example, if you want to show under your add to cart button, start with the Template product.liquid, then work your way through the code to see where the add to cart button is (it's most likely in an included snippet, for example product-form.liquid is common).
3) Edit the file with your code, then preview that theme.
4) Adjust as necessary, then when everything is ready, publish that theme.
If you need help on how to work with themes, here's a guide I wrote: https://speedboostr.com/how-to-safely-edit-your-shopify-theme.
If you want to have a professional developer handle this for you, feel free to reach out to my team at speedboostr.com/contact. We make theme customizations like this on a regular basis.
You can easily sell/import only Amazon products on your Shopify store using this app Spreadr.
Also, if you are looking to import products from virtually any site like Amazon, Flipkart, Walmart, eBay, etc. on your Shopify store, you can use this app Outlink. Both the apps do also have a chrome extension that will help you to import products.