When in a issue view page (e.g. Test Set, Test Execution, etc), you may need to search for other issues to associate to the one you are looking at.

Search Screen

Select Tab

You can search recent issues or use the free text search:

You can search for issues using the various filters Xray provides

If you feel you need more flexibility on your search you can also search with JQL

When searching for issues, you ma want to add only some of the issues found when searching or all issues returned.

Xray provides you the possibility to add selected or all as the buttons shows.