I need help to improve the release process

Hi everyone, I recently took a position as a CTO and I've been enjoying my time while improving the work the team has been making. My biggest struggle right now is how to better release features in production, the team doesn't have a standardized way of releasing features into production and the sales and marketing teams never find out when things are release. I tried to implement release notes but I'm still struggling with the releases because I never know what's ready to be released and what's still on QA process. I've asked the team for their help but I don't think they know what to do. Could someone point me towards the right direction of improving this process? Thanks!