As an Office 365 admin, you have control over deciding what Office software your users get access to. If you have users running versions of Office that are no longer in mainstream support, it is highly recommended that you help them upgrade to the latest versions. You can check mainstream support end dates for Office software on this page.
The steps below will help you upgrade your users to the latest Office clients.
Make sure you have an Office 365 for business plan that includes the latest versions of Office
Some Office 365 for business plans don't include the latest versions of Office. If you don't have a plan that includes fully installed Office on PC/Mac, then your users won't be able to upgrade Office. In that case, you will need to change your current plan or purchase a new plan that does include fully installed Office on PC/Mac before you are able to continue.
Make sure the user you are upgrading has a license
After you have made sure your Office 365 plan supports fully installed Office on PC/Mac, you will need to make sure that you have assigned a license to all the users who will be using Office on PC.
Direct the user to install the latest version of Office
After you've verified that the users you want to upgrade all have licenses, the final step is getting them to install Office. Please read Manage user software in Office 365 to learn about how to let your users download and install their licensed software.