Yes, you're in. I use Flotilla on mobile where you click the three dots at the top and the Groups screen slides out. That's where you click the create room option, give it a name, set the permissions of who can see/read/write to the group. You then send out 4 invites. Each invite you send out can then also invite 4 more people. Each of them, another 4 etc. Or, if you just set the room permission to public, then anyone can join. Or, you set set permission so public can read it, but only members can post.

After you using desktop or mobile? I just tried chachi.chat on desktop and it had way more options than Flotilla. Gives you way more options like embedded videos. Here's a link to a group using Chachi. https://chachi.chat/onlynostr.club/8005261086733322