Using a custom field for Amazon affiliate links
To display a "Buy from Amazon" affiliate link or button in your listings, you need to create a custom field (field type must be "text") that will store the Amazon ASIN number.
ASIN is a unique identification number assigned by Amazon. Example: B001U3Y8PO
To display the affiliate link instead of the ASIN or ISBN number in listing details, you will need to replace the field's default Output Format (under Advanced Options):
Replace the default {FIELDTEXT} with this:
<a href="http://www.amazon.com/gp/product/{FIELDTEXT}?ie=UTF8&tag=AFFILIATEID&creativeASIN={FIELDTEXT}">Buy From Amazon</a>
Then this field will be displayed as a "Buy From Amazon" link.
Replace AFFILIATEID with your affiliate ID that Amazon generated in your account.
If you want to display Image button instead of text link, use this:
<a href="http://www.amazon.com/gp/product/{FIELDTEXT}?ie=UTF8&tag=AFFILIATEID&creativeASIN={FIELDTEXT}"><img src="images/amazon.gif" /></a>
You should upload the amazon.gif image into the Joomla's "images" folder in the root.