AMIMOTO-AMI comes ready with Multisite config settings, however, these settings are disabled by default.
Step 1: Log in as Root
Follow this guide to log in as root on AMIMOTO.
Step 2: Edit NGINX Config
This file will either be the default file or a custom one you've created.
Next, located the line for wp-singlesite and comment that out and uncomment the line wp-multisite-subdir.
listen unix:/var/run/nginx-backend.sock default;
index index.php index.html index.htm;
access_log /var/log/nginx/example.com.backend.access.log backend;
Step 3: Restart NGINX
For these change to take affect restart NGINX.