If you are using IMAP and you cannot see your spam folder it is possible that you need to reset your folder lists. Below is an example of how to reset the folder list.
Assuming that your Outlook us setup as suggested, IMAP and not POP3:
Right click the mail account on the folder list. If you are using Outlook express then select Reset Lists or if you are using Outlook 2003/2007/2010/2013, select Update Folder List.
The Spam folder will now appear under you e-mail accounts folder list.