There are instructions posted over on the DirectAdmin forums, but they're hard to find. Some of those darned topics have hundreds of posts over multiple years... no way to find the one post you want easily.
One of the posters there, @How@, has an "All-in-One" script that is supposed to update just about anything you might want to in DirectAdmin. But a word of warning; for all of his helpfulness, you need to be careful about the scripts he provides as they often have bugs. Use them as reference or run them as is, it's up to you; but a little poking around the script first is called for in any case.
First, download his script:
This page has some information about how to use the script: