how to add a new player to an already on-going game of dread?

hi reddit. so recently I've come across dread and got really into it. I've read the book and tried to host a few demo games with my dorm mates. we are all new to TTRPGs and i thought dread was going to be easier for us to start with.

long story short, we are in the middle of a dread campaign (story?) right now and there is a person (a new player) that wants to join the game. the whole group is okay with this so i don't see a problem adding them to the game. however, i have no idea how to do so.

how can i add them to our game? should i explain the story? in what sort of ways can i add them?

p.s: my story is about a group of students exploring an abandoned sanatorium.