You don't need to know any programming language at all. All you need to know is how to run a Linux server and deploy a tech stack for the forum software you want to use. A complete mouth-breathing moron can do it by following some tutorials for a few hours. For instance, if you wanted to deploy a XenForo board, like this one, you'd need to
set up a LAMP stack (Linux, Apache, MySQL, and PHP). Linux is the OS the server would run, which can basically be any distro, though Debian and Ubuntu are fairly common (when it comes to servers, a stable Linux distro is better than a fancy one). Apache is your web server and actually serves the pages to your users. MySQL is database software and stores the entries representing each post. Having PHP installed provides the necessary prerequisites for the actual forum software itself. You need to get a domain off a registrar and install an SSL cert, too, and then direct your domain to your server's IP with your forum software loaded and running, and voilà. Forum.
ou also need to set up an email server or SMTP relay to send emails to your users. This is absolutely necessary for account confirmation/admin mail purposes. Unlike a personal blog, you CAN'T get away with not having an email, or having the site's email be your own personal email address. The forum system
must be able to send users email automatically.
These instructions vary depending on the forum software. For instance, if you want to run a Node.js based forum like NodeBB, you would need to install a MEAN stack (MongoDB, Express, Angular, and Node). Knowing HTML, CSS, PHP, and JS is very helpful, but it's not strictly necessary. You can do all of this yourself, of course, but if you're a first-time admin, you will probably have absolutely no idea if your server is secure from intrusion or not, or if you're about to have some script kiddie steal all your users' emails and passwords, or replace your whole forum with goatse or something. Since you're running a forum, one of the internet's many gaping assholes, the probability of your board being hacked or credential-stuffed at some point by someone with an axe to grind will eventually approach one.
If you actually plan on becoming a forum admin, I have only one piece of advice.