You can add a discussion in your course room in two ways. You can insert a direct link in one of your modules or publish the discussion course menu link. Another way is to use both of these options.

Direct link in a module

You can add a direct link to a specific discussion thread inside of a module. Let's say you are only going to have one or a few discussions in your course. Then it might be a good idea to add them in the right context via modules.

To add a discussion go to Modules and then the + button to add an item.

Screenshot of empty module.

Choose Discussion from the drop down-list.
Select [New Discussion] in the large box or add a already created topic in the list.
Enter the name of the new discussion.
If you want to indent the topic name in the module, add a value here.
Click Add item. The discussion will then be added to your module but unpublished.

add new discussion

Activate the discussions course menu link

If you want to have different kinds of discussion threads visible during the whole course you also have a choice to enable the course menu link. If you are not using modules or if one or more discussion topics don't belong to specific module, this can be a good way to display and gather discussions.

Click Discussions in the course menu.
Click +Discussion to create and edit your discussion settings.

new disussion from menu