Globo is used to refer to both the free tv channel and the whole media conglomerate (multiple channels, streaming platform, production company, newspapers, etc), that'd probably where the confusion comes from.
The entertainment news website owned by the Globo conglomerate says this about the streaming of the show:
"Transmissão: sexta (15), a partir das 20h30, no Multishow e no Globoplay, disponível também para não assinantes."
Transmission: friday (15), starting at 8:30pm, on Multishow and Globopay, also available for non subscribers.
Multishow is a cable TV channel, Globoplay is a streaming platform. They specify that it will be available for non subscribers, because while Globoplay also streams multiple channels live (including Multishow) only one is free, the others you need to have a paid subscription to watch. But during big events like Rock in Rio, they often make Multishow free to stream as well. From what they said, this is what they'll do for the show. Regardless of whether you pay or not you need to be logged into an account to watch*. All of that is true for people in Brasil.
For people outside of Brasil, I checked a few countries with a VPN (US, UK, Canada, France, Germany) and for those, even the channel that is free in Brasil says it's only available to subscribers. So I think Multishow won't be free to watch that day for people outside of Brasil. Subscriptions that include the Multishow channel are the equivalent to $9.49 and five people can watch at the same time. (inb4 other brazilians reading this, multishow is only available in the premium subscription, not in the cheaper ones.) After you've created an account and logged in, you can get a subscription here , click "Mensal" (monthly) on the center of the page and click the rightmost "Assinar" (subscribe) button. After all that, you can go to Globoplay and watch. On friday, there'll probably be a giant banner somewhere on the front page, but here's a direct link to the Multishow stream.
*You can create an account here.
tl;dr: if you're in Brasil, go to globoplay, log in and watch the show. If you're outside Brasil, create an account, you'll most likely need to pay $9.49, and then you can watch.
Hope this is helpful.