In most cases, you create a project by adding an API so that you can work with it later. However, you can also create an empty project and add an API to the existing project.
Creating Project From REST URL
OpenAPI/Swagger definition (REST)
OpenAPI/Swagger definition stored in SwaggerHub (REST)
WADL definition (REST)
WSDL definition (SOAP)
Creating Empty Project
Project ManagementReadyAPI Documentation