Forums in the MIMO site are generally restricted to those registered for a given program, unless they are general forums for your membership level.
In order to access the forums, go to the user menu at the top-right of the page, after you are logged in, and click the ‘Forums’ link:
You will see in the Forums main page, the forum discussions that you have access to. You may click any of these to read and reply to messages, as well as create new discussions:
You will land on the index page for the forum you choose, so you may read and select discussion titles, or start new discussions:
On the selected discussion page, you have the option to subscribe to the discussion, and receive notifications to your MIMO account, and/or add new messages to the discussion:
NOTE: After clicking the “Reply” button in a given post thread, it will look as if you are replying to the last person who posted, if you’re not on the first page of the discussion. This is ok, and your message will be posted on the end of the discussion but will pertain to the original post.
You may, as an alternative, return to the first page of the thread, by using the page navigation at the bottom of the page, and post (hit reply) from there, making it obvious that you’re replying to the first post in the thread.