When an admin posts a Poll, you can view it in the activity or group feed (depending on where it has been posted in). You can also view and participate in the poll under the Poll app.
To participate in a poll:
1. Go to Apps and then click on Poll
2. Click on the Poll post to view it completely and submit your response
3. Participate in the poll by clicking on the option of your choice. You can view the poll result and react or comment on the post too