You have uploaded the files to the correct directory. When you add a new domain or sub-domain via the panel, a new sub-directory is automatically created for that domain within the home directory of the user that you specified as the controlling user for that domain. This sub-directory will by default be named the same as the domain or sub-domain (ie: mydomain.com).
I am guessing that the DNS information for your sub-domain has not yet fully propagated and this is the reason you cannot browse to the sub-domain yet, it is also likely to be the reason you could not specify the sub-domain when logging in via FTP.
/home/darkedge/ is the home directory for user 'darkedge'.
You can specify any directory you wish as the web-directory for the sub-domain, but you will still access it as subdomain.mydomain.com from your browser.
Edit: By the way, WorldOfAeraea.com is a full domain, not a sub-domain. A sub-domain would look something like WorldOfAeraea.darkedgedesign.com.
To add another full domain to the system, you must first register the domain name, otherwise the domain will not be accessible. Sub-domains on the other hand, only require that the parent domain name has been registered.
Save [color=#CC0000]$50[/color] on DreamHost plans using [color=#CC0000]PRICESLASH[/color] promo code (Click for DreamHost promo code details)