Assuming that you already having an Amazon account, there are several ways that you can use Amazon links in your posts.
You can use Amazon’s pictures in your posts and then link the pictures to the product. You will need some sort of screen capture program to take a picture of the item and then save it to your computer.
Watch this video to see how to add the picture and use an Amazon link:
2) An in text link:
You can get the link in the same way that I recommend in the video. Then, highlight the text that you want to be linked to the product, click the link icon at the top of your post editor, and paste in your Amazon link.
These are the simplest ways to add Amazon links in your posts.
Any iframe code that is provided by Amazon does not work well with WordPress. It might work sometimes but most of the time the code will be stripped and it will just not appear right.