Don't wait until the final minutes of your live session to post a CTA button. Use them throughout the live stream, particularly during the following moments:
When audience numbers pick up at the start of the show
After describing a product
When you notice a surge in viewership during mid-broadcast
After answering a viewer's query or a series of queries
Following a milestone such as "The 10th piece of (product so-and-so) has just gotten sold..."
Train your audience to note and remember your website and other important links. Give them time to take a screenshot of the CTA containing your contact information and pause for a few seconds to let them do so.