In order to enable a project to be a Requirement Project, you just need to make sure that the Test Coverage is enabled.
You do that, by identifying the Coverable Issue Types.
Access your project settings > Xray Settings > Test Coverage
Perform the desired mapping and Click "Save"
Info
This module details the minimum configuration that needs to be done to create a new project with Requirement Coverage enabled. Go to Basic& Cloud Advanced Setupto explore other configuration possibilities.