I tend to add my footnotes in the flow of the text, usually directly after the paragraph that requires the footnote. I know, I'll probably be laughed off the forum for doing it this way, but it works for me, and I don't need to be jumping around my novel trying to read references. Plus, general fiction novels that require footnotes are an exception, rather than normal, and there aren't many of them.
But no reason you couldn't place the footnotes elsewhere using the same code.
For the example in the image, this is how I code it...
PHP Code:
Greenland.<a id="p01c06" href="p01c06.xhtml#p01c06a"><sup>1</sup></a> The <em>reality</em>
PHP Code:
<p class="footnote"><a id="p01c06a" href="p01c06.xhtml#p01c06">1</a> P. Chylek, et al. 2004