1)Manually searching for players by using a max age and setting key attributes filters in the player search.
2)Scouting international youth tournaments (E.G. U19 World Cup).
3)The most time consuming, but most effective way (In my opinion) is to click on the globe icon (Top of the screen) then click on 'Transfers' then 'World' in the drop down Menu. Then in the top left where it says 'All Transfers' change that to 'Youth Intake' and just have a quick look at the players there
(In case that last one was a bit confusing, this is a simpler way of saying it:
Globe>Transfers>World>'All Transfers' to 'Youth Intake' )