Hi Kirby,

To be technically true, you can't really "point a domain to a subfolder", put you can point a domain to an IP, as required by DNS to go on a website using a domain name instead of its IP.

So, in your situation, I much advise you to use Nginx as a reverse proxy, thanks to the use of server_name directives and document root location.

For example, if you want to host many websites on your VPS at IP 111.111.111.11, you can create as many folders you want in /var/www folder, and configure all your nginx virtualhosts to point the correct folder.

tree /var/www/
├── drupal_1
├── drupal_2

Once you have the following tree in your document root, you can use server_name directives to separate your drupal instances relied to a domain name with Nginx, with a configuration file of that kind :

server {
  listen *:80;         
  server_name drupal_1; 
  root /var/www/drupal_1;

  location / {
    try_files $uri $uri/index.html $uri.html @upstream;
  }

  location @upstream {
   your php-fpm configuration
  }
}
server {
  listen *:80;         
  server_name drupal_2; 
  root /var/www/drupal_2;

  location / {
    try_files $uri $uri/index.html $uri.html @upstream;
  }

  location @upstream {
   your php-fpm configuration
  }
}

Thanks to that kind of Nginx configuration, I guess that you will be able to do what you are looking for,

Hope this could help,

Best regards,

--
rustx

To expand rustx already detailed answer if you are not using Nginx the process is pretty similar in your domain manager/control panel simply point your AAAA record to your VPS IP Address and wait for it to refresh and start redirecting the domain to your VPS local folder than:

Open file: /etc/apache2/sites-enabled/000-default.conf

Or you can create a separate configuration file as you prefer I keep all my VHosts in one file. Once you have the configuration file open add new VHost configuration like so:

<VirtualHost *:80>
    DocumentRoot /var/www/subfolder
    ServerName www.domain.com
    ServerAlias domain.com
</VirtualHost>

Now go back to the folder: /etc/apache2 and open file: apache2.conf and add a new line:

ServerName www.domain.com

Save the file and restart your server using this command: service apache2 restart, the process is same across all OS the config folder locations tho can be different you can look those up.

@SterlingDuches That worked perfectly for me.
I just have one problem. When I type www.domain.com I get a " page not found ". Do you know how to solve this?

Thanks in advance.

@Joaobborges Setup your CNAME record to catch www too:
https://www.digitalocean.com/community/tutorials/how-to-set-up-a-host-name-with-digitalocean

(long tutorial, just scroll down to the CNAME section)