They must notify the visa office well in advance, bye mail at visamail@justice.ie giving complete details of the event, schedule and dates of performance, the reason for engaging the applicant, how they came to know about the applicant, and if the organizers can vouch for the bona-fides of the applicant/ group, the same should also be indicated.
The event organizers should also inform the visa office as to who will be responsible for covering the travel, accommodation and living expenses of the applicant/ group during their stay in Ireland.

Documents required by the applicant
Fully completed and signed Visa Application form (in duplicate). See Annexure Ireland-I
Two passport size photographs.
Required visa fee
Any previous passports
Enclose original and one photocopy of the following: .
A valid work permit or written confirmation from the Department of Enterprise Trade & Employment in Ireland that a work permit will be issued, or is not required.

Evidence of how trip will be funded - who will cover cost of travel, accommodation and expenses.
Note:
1 It is advisable that the applicant have a medical/ travel insurance covering the entire duration of visit.
2 All letters submitted should be on official company headed paper giving complete contact details for verification purposes. These must include a full postal address, name of contact person, his/her position in the company, telephone number (landline) and email address where relevant. (Email addresses such as Yahoo or Hotmail are not accepted).
Website address should also be included, if available