Specify time: "1h2m3s" (replace the time of course) in the options object.
For example:
var options = {
width: 854,
height: 480,
//channel: channel,
controls: true,
video: "v83196893",
time: "1h2m3s",
quality: "low"
};
var player = new Twitch.Player(id, options);