Instagram does not support RTMP live streams from a computer without using 3rd party software. Even with this software, the video is cropped to a 9:16 ('portrait') frame that may crop out some participants in the Riverside Studio.
TIP: Export Video for Social Media with Vertical and Square Aspect Ratios
Use Riverside's Editor to change the aspect ratio of recorded clips, including 9:16 or 1:1, to share them on social media. You can also arrange and trim the videos before exporting them.