The Asterisk Manager Interface is configured with the file /etc/asterisk/manager.conf. There’s not much to the file. The general section is used to configure if it is turned on and what ip / port it runs on.
Other than that you just need to add users that are allowed to connect to it. The user name goes in brackets, and the password is specified by the secret tag. There are also permit and deny tags which can be used to specify what IP networks are allowed to connect. 99% of the time you only want to allow the manager interface on the localhost because all communication across the manager interface is insecure and in plain text. The last two tags are the read and write tags. These give your user the ability to perform certain tasks via the manager interface. The possibilities are system, call, log, verbose, command, agent, user, and all. I don’t recall what each gives permissions for but I’m sure you can find that on google or someone else can follow up with that.
port=5038 ; Make sure this TCP port is open on your firewall