Unreal Engine + Websocket + SSL Certificate

Here is an insallation I manage to create :

Unreal Engine is a graphical video game engine.I've installed a plugin which can create a websocket server and a websocket client.So I can perfectly make communicate my web app on a smartphone with Unreal on a local network.

The only thing is I don't know to manage the certificate SSL in Unreal side, as I connect to my webapp through HTTPS, so Secure Sockets are mandatory. So I tried self signed certificate but of course I got this error : ERR_CERT_AUTHORITY_INVALID

Do I need to create a my own Certificiate Authority Server ?

If you want more info about the plugin:https://www.unrealengine.com/marketplace/en-US/product/websocket-server

Any advice ?Thanks.