System administration is a different skill than software coding, although there is some overlap. You should be technically minded and detail oriented, willing to read documentation and tutorials closely, and have the curiosity to dig into related details that you don’t understand. In many ways it’s “just” configuring and running software on a Linux server, but there are lots of details underneath all that (hosting, DNS, backups, security, etc). Of course it’s also then managing users as an instance admin, and presiding over deeply held opposing community views like whether to enable downvotes.

Edit: based on another comment I reread your question and maybe you’re just asking about creating a new community on an existing instance, not hosting your own instance. If so, then my above answer is irrelevant, sorry. Creating a community is very straightforward, you just have to be willing to be the head moderator and deal with everything that entails.