...
To add a test case to the test cycle, you need to click on the menu [...] menu next to the test case name in the Jira issue and then [+ Add To Test Cycle], then . Then a modal window will appear in which you will select the test cycle.
...
Add test case to test cycle from Test Cycle page
It It’s also possible to add test cases to the test cycle directly from the Test Cycle page.
...