Please note that Core must first be added/entitled in your Epic Games Library before being able to launch on GeForce NOW. Install on GeForce article here
Once you have added/entitled Core in your Epic Games Library, you will need to add it to your GeForce NOW Library:
1. Search for "Core" within the GeForce NOW app.

2. Click on the Core image to open the pane and then click + Library to add Core to your GeForce NOW library.

3. You may be prompted to log in to your Epic Games account - if so, click Continue.

4. Return to the main page of your GeForce NOW app - Core should display under My Library. Click Play to launch Core.

5. Login with your Epic Games credentials (if prompted).
6. Play Core!
GeForce NOW system requirements for each device can be found here.
For questions and issues with GeForce NOW, please visit NVIDIA's GeForce NOW support page.
For questions and issues with Core, you may contact support to submit a request.