Seating the rear derailleur cable housing
Set the shifter to the slackest/highest position.
With the bike's rear wheel off the ground, put one hand on the body of the rear derailleur and push while turning the cranks with the other hand.
Push the derailleur until it shifts all the way up to the biggest cog and let go of the cranks and the derailleur.
Put the ferrule in the housing stop.
Turn the cranks a few times to let the rear derailleur return to the smallest cog.