How do I access Kyoubai, the Forumwarz auction house?
You are given a bookmark to Kyoubai fairly early into the Episode 1 story. If you simply continue through your missions, you will receive a Tubmail about it and you will be able to participate.
Specifically, this happens after you pwn Rice, Rice, Baby.
The bookmark will appear under Bookmarks > Services.
If you can't find your problem in the knowledge base, please
submit a bug report.