After your live broadcast ends, tap View Insights and wait for the data to appear. Instagram will display the following metrics:
Reach: accounts reached or accounts engaged (number of users who viewed part or the entire live session) and peak concurrent viewers (number of viewers watching during the broadcast's busiest point)
Live interactions: comments and shares
You can also go to Profile and click the Insights button.  Tap the live video you want to check for analytics then click View Insights.