First, go to the forum. (Learn How at this topic: Basic Navigation
If you are on the Forum overview page, look for the Actions menu on the right side of the banner. Click Discussion.
When you create the topic, remember to identify whether it is a discussion or a question.
You can also add tags to your discussion, so you or other people can find it easily by searching, without having to navigate.
Visit the AMD Community FAQ for this and many more answers about how things work around here.