Hi,
Greetings and welcome to Intel's forum.
I have here a few projects for you to try out for beginners:
1)You may check out table 3 Intel Arria 10 Downloadable content like the Board Test System so you are familiar with the board hardware architecture and ensure it runs:
https://www.intel.com/content/www/us/en/products/details/fpga/development-kits/arria/10-gx.html
2)You could try the Board Update Portal Example Design which is to bring up an IP address on the board where this design consists of a NIOS II processor:
https://www.intel.com/content/www/us/en/docs/programmable/683553/current/board-update-portal.html
3) I also have a Hello World which applies for Arria 10 Soc for your reference for you to see the flow of how to create a working NIOS Software and Hardware project but it might not be able to apply for your Arria 10 GX DevKit.
Feel free to head to our FPGA Design Example Store to find out any design examples that you might be interested: https://www.intel.com/content/www/us/en/support/programmable/support-resources/design-examples/design-examples-overview.html
Hope you could explore about NIOS II and looking forward to your feedback.
Thank you.
Regards,
Kelly