Customizing means editing rows and columns; you can add or remove rows and columns as you deem fit. A blank spreadsheet has hundreds of uses. If you cannot figure out how to use the template, try to do more research on 50 ways to use Sample Spreadsheet Templates.
There are more than 100 ways to use Google Spreadsheet template, including keeping records of contact details, synchronizing WhatsApp texts and contacts and data analysis. Google sheets are great alternatives to MS Excel, and you can use them even on your smartphone devices. You can download the spreadsheet from the internet for free.