Consider reading through this good guide by @jprspereira:
TL;DR Guru the radicals and you will get kanji. You guru a radical by doing the review after certain timeframes.
Here are the timeframes and how long you will have to wati:
Apprentice 1 => Guru 1 (3d10h, considering 4 correct answers in a row)
Apprentice 1 (lesson)
Apprentice 2 (+4h)
Apprentice 3 (+8h)
Apprentice 4 (+23h => consider this as 24h or 2x12h)
Guru 1 (+47h => consider this as 48h or 4x12h)