Help- utilizing DAC on Hegel. Integrated over OPPO

Hi,

Need some help and advice. I own a Hegel. Integrated and an Oppo. 105. Obviously both have Dacs and I stream a lot of my music via OPPO however I want to utilize the DAC in the Hegel. Over DAC in Oppo. Was told I need an SPDIF cable? Is this correct? If so once connect SPDIF cable how do I tell OPPO I want to stream everything through HEGEL?

STEP BY STEP would be helpful.

Do I need any other cables?

Thanks in advance