You can use Advanced Sessions and Advanced Steam sessions, but I don’t recommend you do that. You will then tie yourself to the Steam ecosysstem, and you might publish your app on GOG, for example. Then you will have an issue. It’s much better to use Epic Online Services to setup and manage achievements. it’s quite easy. You can find bunch of tutorials online. If you want to stay away from C++, you can try this also:
https://www.unrealengine.com/marketplace/en-US/product/achievement-system-blueprint-compatible?sessionInvalidated=true