Getting your players in
Send them the invite code from your campaign page. They put it into Join a campaign and they're in.
That's the whole thing. It's free for them, always, and there's no approval step for you to forget about.
Sending the code
The code sits on your campaign page with a copy button and a share button next to it. Share opens your phone's usual share sheet; on a laptop it falls back to an email.
Do they need an account first?
They'll need one to join, but they can make it on the way — the code still works after they've signed up. It's fine to send the code first and let them sort themselves out.
Worth saying in the message: players never pay for anything. It's the first thing people ask when they're sent a link to an app, and the answer is a flat no.
If the code gets out
Backstage has Regenerate invite code. The old code stops working immediately and everyone already in stays in.
When that's worth doing
The code is the only thing standing between your campaign and someone who has it, so treat it like a door key rather than a username. Posted it in a public channel, or in a group chat that's grown since? Regenerate and re-send. It costs nothing and nobody in the game notices.
Seeing who's in, and removing someone
Backstage lists everyone who's joined under Players, with a remove button on each.
What removing someone actually does
Their character splits in two. You keep a copy in the campaign — moved over to the Cast — so the story doesn't develop a hole where they used to be, and they keep a copy of their own that they can take to another game.
From that moment the two are unrelated. Nothing you do to yours reaches theirs.
Their private notes go with them, which is not something you can change and not something you should want to: it's the same rule that lets your players write honest things down in the first place.
It works identically whether they left on their own or you removed them. There's no punished version.
Someone joined twice, or joined the wrong game
Remove the spare from the Players list. If they'd already made a character on it, they'll keep a copy of that one too — a bit untidy on their shelf, harmless everywhere else.
This is help for ACT VI: The Tabletop Turns — a system-agnostic companion app for running tabletop RPGs. Players never pay, and a GM's first campaign is free.