Custombuild 2 allows us to have a reverse-proxy NGINX + Apache on Directadmin powered server without a need for any 3rd party scripts or plugins, addons. That's quite easy to start using it.

CustomBuild 2.x version

First of all make sure you've got custombuild 2:
cd /usr/local/directadmin/custombuild
./build version
You should see an output similar to the following:
[root@server custombuild]# ./build version
2.0.0-RC7 (rev: 863)