Using a custom field for Amazon affiliate links
You can create a Text custom field to submit Amazon ASIN numbers and modify the field's output format to display the field as affiliate link instead of the default output (ASIN number).
ASIN is a unique identification number assigned by Amazon. Example: B001U3Y8PO
For books, the ISBN number is used instead.
To display the affiliate link instead of the ASIN or ISBN number on your site, you will need to replace the field's default Output Format which is available in Advanced Options.
Under the Output Format replace:
{FIELDTEXT}
with this:
<a href="http://www.amazon.com/gp/product/{FIELDTEXT}?ie=UTF8&tag=AFFILIATEID&linkCode=as2&camp=1789&creative=9325&creativeASIN={FIELDTEXT}">Buy From Amazon</a>
Now this field will be outputted as a "Buy From Amazon" link.
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&linkCode=as2&camp=1789&creative=9325&creativeASIN={FIELDTEXT}"><img src="images/amazon.gif" /></a>
You should upload the amazon.gif image into the Joomla's "images" folder in the root.