How to Activate Archives and Their URL?

Archives are a native thing generated automatically by WordPress. You don’t really activate them.

These work fine for me:
http://mydomain.com/2009/09/
and
http://mydomain.com/2009/

Might try updating your permalink structure via Administration > Settings > Permalinks. Note: I used Day and Name

I’m becoming very frustrated with WordPress. I’m a quick learner but some things are just not explained fully or adequately. I’ve asked several questions (some long, some short) in this forum over the last year or so and have NEVER gotten a response, so I hope this time will be different.

I’ve just been searching and reading for over an hour and I still can’t figure out how to create an archives page. I don’t understand why WordPress doesn’t have some kind of Archive index page already set up by default. When I go to http://www.MyDomain.com/archives/ I get a 404. I’m using a custom permalink structure:
/%postname%/%post_id%/
and the All-in-one SEO plugin, and I don’t want to change either one.

There should be a topic in the Codex like “How to set up your archives.” The closest thing I could find is: “Creating an Archive Index” (http://codex.wordpress.org/Creating_an_Archive_Index).
It gives instructions for “WP1.5” and “WP1.5+”.
If the instructions for WP1.5+ don’t apply to recent versions of WP, it would be nice if someone would modify that page and say which versions the explanation applies to. It says “In the sidebar open the Page templates box, and select the Archives template.” But there is nothing like this in recent versions of WP. The previous instruction is to create a new page called something like “Archive Index.” (Again, why doesn’t that page already exist by default?) I did that, naming the URL http://www.MyDomain.com/archive/, but it’s not clear what I’m supposed to do next, because I can’t find anywhere in the admin panel any place to select the Archives template or anything similar. Surely I’m not supposed to add php manually to that page! (e.g., <?php wp_get_archives('type=monthly'); ?>
cf. http://codex.wordpress.org/Pages#Archives_with_Content)

So the Codex for this issue (setting up an archive page) gives step-by-step instructions that are apparently years outdated (but don’t say so), but this page (/support/topic/315629) says there’s nothing to activate.

My theme (“this just in”) comes with a commented-out link to /archives/, but as I said above, this returns a 404. It’s not at all clear to me how archives.php and archive.php in the theme folder are utilized. I can’t find anything in the admin panel that relates to archives.

All I want is a page that has a list of past posts by month. My theme indicates that it ought to be at /archives/; here’s the code:
<li><a <?php if(is_archive() || is_page('archives')) echo 'class="current" '; ?>href="<?php bloginfo('url'); ?>/archives/" title="Visit the archives">Archives</a></li>

…but since there’s nothing at that URL it’s obvious something has to be done for it to be “set up” or “activated.” I just haven’t been able to find an answer in the Codex or the related support forum topics.

PLEASE HELP!!

I am having a hell of a time getting my Archives list to bring up the old posts I brought from Blogger. Clicking on a Month brings up this message:

“Fatal error: Call to undefined function the_post_thumbnail() in /home/aard6315/public_html/marikane.com/wordpress/wp-content/themes/atahualpa/functions/bfa_post_parts.php on line 124”

What does this mean?

I know the archived posts are there, as they can be accessed through search engines. I just cant get my page’s Archives list to bring them up.

Please, somebody, throw me a bone here!