When you are using Google Forms you can find and install new Add-ons as follows:
Source: Eric Curtis (Ctrl Alt Achieve)
How to use installed Add-ons
Once you have installed an Add-on, it will show up in the drop-down menu when you click the puzzle piece icon in the top menu bar. To use an Add-on:
Equatio- Add math equations right into your Forms
Choice Eliminator- Remove choices after people select them
Forms Limiter- Limit the number of responses you get for questions
Data Director- Saves Form data to multiple Google Sheets, creates calendar invites and does more with PDF's and other Sheets
AutoMastery- Sends students work based on their scores on Google Form
Chatbot Build a chatbot app based on Google Forms
Form to Calendar Turn form responses into a Google calendar event
Control Accepting Responses Stop accepting form responses at a certain date, time and/or number of submissions
Gift Quiz Editor Create quizzes with the GIFT syntax
Certify'em Generate certification for every candidate that passes a test
Sources: Zapier and Make Use Of