First you need to open the Google trends tools https://trends.google.com/trends/ and you will see the search option, you could select the already trending topic from the list or enter your own.
Google trends would automatically break down all details and analyze them for you.
You will get an index from 1-100 for the number of times your topic has been trending
You will get an option to get results according to sub-regions and City
As you scroll down you will see results for more related topics and queries
This feature allows you to compare results to more than 2 topics