At the end of each season the draft takes place in the North American championship.
By default each team has two choices in this draft, a first round and second round. The order of selection of teams is determined by random selection based on the ranking of the teams, the lowest ranked teams are more likely to choose first.
You can only draft players who chose to attend. Players who present themselves are mostly players from US universities but some are from national championships.
You have no influence on the agreement of the players you draft that will be on "Rookie exception" and a salary depending on the position in which he was drafted.
Note that you can include draft picks in trades, their position will be determined by the position of the team who originally owned the round pick.