This guide will explain how to get osu! song requests working on your channel.
First thing you'll have to do is enabling the osu! plugin here.
Go to osu! plugin settings here.
Find the username field and click the link below it.
Now, open osu! and write "!verify" to MikuiaBot.
Easiest way to do that is by using "/msg MikuiaBot" to open a conversation, and then using !verify.
Put the code on the website you opened earlier, and click Save.
You should be redirected back to the settings page, and your username field should be filled out.
Global requests are enabled by default, so if you don't want to change anything more, you should be good to go.
You can also enable or disable the request information on chat, limit requests to subs, set request limits, and more.
Before you start testing, remember to disable the "Ignore Myself" option, or use a different Twitch account.