Assuming:

• you have running prosody.im XMPP server
• you have the telnet module enabled
• you added modules and/or changed configs
• you don't want to restart the service and force-disconnect the connected users

Here is what you do:

telnet localhost 5582

now we want to load a module

module:load("muc_log", "conference.example.com")

| Loaded for conference.example.com
| OK: Module loaded onto 1 host

if loaded first time just do

module:load("muc_log_http")

more trickier, when you need to clean up for a module reload

httpserver.new.http_servers[5290].handlers["muc_log"] = nil

now browser to http://conference.example.com:5290/muc_log/ (trailing slash needed!)

now: profit!