Saima,
Try this: in your course go to Settings, Apps and search for Twitter. Click the Add button to add a twitter integration. Now anywhere you have the Rich Content Editor such as a Page, click the blue V to access External tools and you should see Twitter as an option. You can search by hash tag or user to create the embed.
For me that has been about the only way to make it work. Twitter's web site has some additional methods to get embed codes, but unfortunately the type of embed they use gets stripped out by the Canvas rich content editor.
Rick
This discussion post is outdated and has been archived. Please use the Community question forums and official documentation for the most current and accurate information.