Once the Add-on has been added you will then need to enter into your Google Slide and select Add-on> Slido.
Once Slido is selected you will then have the options to add a question with options for the audience to answer. Once ready you will need to select Present with Slido and be presented with the poll, code for your audience to type into sli.do and see live results. Participants can also ask questions. Embedded below is a screenshot showing what the results look like as well as a 1 minute and 59 second YouTube tutorial.