You have to enter a voice call from another device, either your PC or your phone. Once you're connected, you can "transfer" the call to your PS5 from the other device. Once transferred, you can access audio controls or leave the call via a card in the PS menu. If you leave the call, you have to join it again from the other device and transfer it back to your PS5 again.
It's a bit cumbersome, but it gets the job done and gives you better audio quality than you'd get from bluetooth. I use a Sony InZone headset, so the audio from the PS5 is from its own wireless protocol with a USB dongle, instead of bluetooth.
Being able to do it all straight from my PS menu is going to be a huge relief, because I'm tired of annoying my friends by joining a call, and being silent for another 20 seconds while I transfer the call from my phone.