After installing Xray, there are basically two steps you need to make or ensure before starting to use it.
Configure Requirements and Defects
In Jira's administration, in the Add-ons tab, go to Issue Type Mapping and configure what issue types should be considered as "requirements" and "defects".
Learn more
Refer to the specific Issue Type Mapping page or take a look at the extensive Administration Settings if you want to fine-tune Xray or adapt it to your specific needs.
Enable Xray in your projects
You can enable Xray for your existing projects or create a new project with both standard and Xray issue types.
For existing projects, in the project Administration page, go to Actions at the top right-hand side. You can either:
a) set your project as a Requirements project by choosing "Enable Xray Requirement Coverage", so the requirements are covered by tests; or
b) add Xray issues (i.e., Test, Test Set, Test Execution, Test Plan) to the project.
Learn more
If, instead, you want to quickly create a new project and use it to manage everything (e.g., requirements, defects, tests), go to the Jira Administration page for Projects. In the creation dialog, choose "Xray Test Project".
Learn more