OK, in looking at the code for my site, I see it's a bit more, um, interesting than I'd remembered, but here goes:
In your admin panel, click on Forums at the top of the page.
Then, on the left, click on List All. You'll get a list of all your categories and forums. Click on Modify next to the category you want to add the meta tags to. You'll get a form, at the bottom of which you should see blank text boxes for those new fields you've created. Add in your description and keywords. Click on Modify Record at the bottom, then repeat this process for each category for which you want to add that meta information.
When done, edit your category_list.html template (I think I wrote category_view.html before, sorry about that!). Somewhere between
insert something like the following:
Code:
<%ifnot main_page%>
<%loop everything%>
<%if cat_description%><meta name="description" content="<%cat_description%>" />
<%endif%>
<%if cat_keywords%><meta name="keywords" content="<%cat_keywords%>" />
<%endif%>
<%lastloop%><%endloop%>
<%endif%>
For some reason, you need those loop statements for categories but not for forums. My apologies for not remembering that - this is why I should leave stuff like this to the trained professionals :-).