How to make a docker image for existing/already installed applications

Dear experts,
i am new with docker and want to create an image for my already installed applications like nginx, nodejs and react js.
brief background, i have a linux server (centos 7), its running with nginx with nodejs and reactjs applications. How can i make a docker container for these applications. i want to shift these applictions to other environments where there is no internet access on the running servers so no pull from docker hub.

kindly suggest.

thanks in advance.

Pankaj