This is clearly given in the chapter B07 of the FIDE Handbook and reads as follows:
4. Licenced Trainers:
4.1. All Head of Delegations/Captains/Coaches/Trainers at official FIDE events such as Olympiads, World, and Continental, Team Championship, and World and Continental Junior and Youth Championships, are required to be licenced trainers.
4.2. Only licenced trainers are allowed access to the official playing venue and playing area (as the tournament regulations allow) and be entitled to free board & lodging (where it is offered by the organisers).
4.3. If a Federation is unable to organise for a licensed Head of Delegation to fill a position at an official FIDE event, dispensation can be granted, although only in special circumstances. The process for dispensation includes: a) a written application to TRG with detailed motivation, b) a conversation with a representative from TRG, and c) a one-off fee of €400 (four hundred euros) paid to the FIDE Treasurer in advance.