When the requirements for a project are neither being maintained in Test Collab nor in the issue manager that is integrated with your Test Collab instance, then you can get them managed by opting to keep the "External Tool" as the source of requirements for your project.
Enabling Requirements Management for Project
Navigate to Requirements tab under Settings menu for the project,
"Enable" the requirements management,
Select "External Tool" as source of requirement,
Type the "Link Pattern", the link pattern should be a valid URL that can be used to point to a particular requirement in the tool. Requirement's identifier would be represented by [[id]] because at the time of parsing this URL [[id]] will be replaced by the actual id that you provide to link with test case in your project.
Linking Requirements with Test Cases
You can provide one or more requirements separated by comma for a test case. and any number of test cases under the project can have requirements linked to them.
See All Requirements Linked in Current Project
Once you have requirements linked with test cases then navigating to "Requirements" menu will show you all those requirements.
On requirements index you can :
Get the requirement opened in the external tool when you click on the requirement id,
See the number of test cases linked with each requirement listed,
Delete the requirement,
See the linked test cases on test suites and test cases management screen