Create custom sensors

Hey, I’m fairly new to HomeAssistant and I’m trying to set up my dashboard atm. I got both my HA and my OMV server on raspberry pi’s and I would like the data shown on my dashboard cards to match better. Is it possible to add sensors, like for instance if I also would like to monitor my OpenMediaVaults processor temperature. That option wasn’t included in the OMV integration, so if it’s possible, how do you create your own?

What is this omv integration? Can’t see it here Integrations - Home Assistant

it is in HACS

Ask on the custom integrations github.