Complex sentence: Entitled persons who wished to leave were instructed to assemble at the Mamy Yoko hotel, from which they would be helicoptered to the airport by Chinooks and from Lungi they would be flown to Dakar.
Split into simpler sentences: Entitled persons who wished to leave were instructed to assemble at the Mamy Yoko hotel. From there, they would be helicoptered to the airport by Chinooks and then on to Dakar.