How do people celebrate holy Saturday?

Not sure what you mean by Easter Saturday, if you are referring to Holy Saturday: the Saturday before Easter, then that day is a day when you should be continuing the fast and abstinence from Good Friday, up until dark, when the Easter Vigil begins with the lighting of the Easter First, then the Exsultet

is sung, and all those readings from the Old Testament that trace salvation history are read - nine in all, only then the lights come on in the Church, and the Gloria is sung for the first time since Lent began - Alleluia, Christ is risen. Then, after the homily the people coming into the Church are baptized and confirmed, and then the Mass continues as normal.