It will take several days. Just go sit with them the first day. Do not reach for them at all, just sit there quietly, not moving much. Drink a cup of coffee or tea. Next day, sitting in the same place, sit there maybe 5 minutes, then toss a little scratch, just so they naturally step closer to you, in order to eat it. Don't give a lot, just a little, sit a little longer, and then go, do not reach for them.
Next day, same game, this time, feed them twice, the first time where you threw it the day before, let them eat it and wait, then a little more, a little closer to you, not right next to you, but closer than before. Wait a while and then leave.
Now pretty soon, when you come in, they are going to be coming towards you, on their terms, but they are looking for that treat. As they come closer, feed a little, wait, feed a little more. The temptation will be to reach for them but don't, that will scare them. Just sit quietly. and pretty soon, one will jump in your lap.
Thing is, some will never really be lap pets, but a few will. Do be careful they don't peck either your earrings or eyes.
I don't hold mine, I did train a group, but over the years, I find I would just rather watch them, I seldom handle mine.
Mrs K