That would be done in the cart too. Basically anything you want to show up on your existing website is done through the cart. If you wanted a page that was completely separate from your website (different design, no link to it, etc), that would be done outside.
The cart is built in a way so that pages without products can't be placed in the categories area. However, we can try a couple different things to get it there anyway.
1) You could create a new category and, instead of adding products to it, you could leave it empty and just place your info on the category page itself.
When you create a category, the area looks like this:
That last box, the Header Tags Categories Description box, can be used to place any amount of text on a category page. The box accepts plain text as well as HTML, so if you want to make it look really different, you could type up your page over in the Page Editor's html editor and copy the source code over to that box.
The only downside is that the very bottom of the page would either show a message saying that you have no products in the category or you would have to put one or more products in it. You could just copy a few over to duplicate themselves in this category if you wanted.
You could remove that message from being shown if you really don't like it. To do that, you will need to edit the includes/modules/product_listing.php file. To get to that file, go to the Tools link and click on the Define Languages link. You will see a button at the bottom for the File Manager. Navigate through the file manager through the includes folder, the modules folder, and click to edit the product_listing.php file.
Closer to the bottom of the file (around line 148), you'll see this:
$list_box_contents[0][] = array('params' => 'class="productListing-data"',
'text' => TEXT_NO_PRODUCTS);
Change it to this:
$list_box_contents[0][] = array('params' => 'class="productListing-data"');
Or, you could go with a different way of doing it:
2) You could create a page over in the Page Editor and set it to the off position. Then, you could manually go into the php file for the categories box and add a link to the new page. To get to that page, go to the Tools link and click on the Define Languages link. You will see a button for the file manager. Navigate your way through that into the includes/boxes folder and click to edit the categories.php file. Towards the bottom of the file, find this:
$info_box_contents[] = array('text' => $categories_string);
and change it to this:
$info_box_contents[] = array('text' => $categories_string .
'<a class="infoBoxContents" href="http://link1.com">link 1</a><br>' .
'<a class="infoBoxContents" href="http://link2.com">link 2</a><br>' .
'<a class="infoBoxContents" href="http://link3.com">link 3</a>');
Of course, replace the links and link text with what you are linking to. Note that the last link you use must end differently than the others.
The downsides here are that this is the more involved way to make the pages and that you can't order your links as easily. The added links you create can't be used within the category links. They must be above or below the categories. In the other option explained above, you would be able to arrange the links in any order you want.
The advantage is that you won't have the message about there not being any products in the category.
Let me know if you have any questions or need any help.