Before getting started, please take some moments to see the terms and concepts and how Xray for JIRA implements them.
Whenever we're dealing with Test Management/QA, a key feature is the association between tests and requirements or defects, so you can keep track of the current status of your project. Xray uses JIRA issues and makes extensive use of them, so you mostly use Xray as you do for your normal daily usage of JIRA.
Finally, Xray for JIRA may be used in different project scenarios, depending wether you want to manage your requirements and tests within the same project or not. You may adopt a test process that allows to fully control your testing lifecycle or you can always decide to adopt one more simpler, even in a per project basis. Teams and organizations usually decide what best suits them and Xray's flexibity allows you to implement it.
You are now ready to install and configure Xray, if you haven't done already.