Your team will need to create all the Xray issues inside the project you are enabling to use Xray.
For this to happen, you need to make make Xray issue Types available in your "Issue Type Schemes.".
You may want to include Xray issue Types ( such as Test, Test Plan, Test Set, Test execution) to your already created created Issue Type Schemes. This will enable you to use Xray in existent existing projects that are currently using those schemes.
Go to JIRA Administration > Issues > Issue Type Scheme and select the Issue Type Scheme you want to add Xray Issue Types.
Drag-and-drop Xray Issue Types: Test, Test Plan, Test Set, Test Execution, Pre-condition & Sub Test Execution to Issue Types for Current Scheme.
Tip
Your team does not have to use all Issue Types at in their project. If you want to go for a simple approach you might only use - Test, Test Plan & Test Execution.
UI Step
Add Xray issue types to your Issue Type Screen Scheme
Your Xray Issue Types need to have the correct custom fields available. In order to do this, you will use the regular Jira setting - Screens.
In order to make this possible, you need to associate each issue type with the correct screen inside your "Issue Type Screen Scheme." . This This will enable you to use Xray in existent existing projects that are currently using those schemes
Go to JIRA Jira Administration > Issues > Issue Type Screen Scheme and select the Issue Type Screen
Click on "Associate an Issue Type with Screen Scheme"
Select Test for Issue type and Default Xray Test Screen Scheme for the Screen Scheme.
Repeat this action for Pre-Condition with Default Xray Pre-Condition Screen Scheme, Test Plan with Default Xray Test Plan Screen Scheme, Test Execution with Default Xray Test Execution Screen Scheme, and Test Set with Default Xray Test Set Screen Scheme.
The final result will be something like this for the Xray Issue Types.
Tip
There is a much faster way to "Add Xray Issue Types" to your schemes.
Go to the Project Settings and set "Add Xray Issue Types." . This will add Xray Issue Types to the schemes used in that specific project.
This is faster, but you have to make sure that:
You are part of the users allowed to perform this operation. Check if the setting at Jira Administration > Manage Apps > Miscellaneous > Users Groups allowed to add Xray Issue Types contains, for example, the jira-administrators group.
You realize the impact of changing an Issue Type Scheme & and Issue Type Screen Scheme directly from a project. Don't forget that the schemes may be shared with other projects.