Bishop Peter Ingham will join 80 bishops and priests from throughout the world on stage at WIN Entertainment Centre for a Commissioning Vigil Mass, during which pilgrims will be blessed before they set out for World Youth Day.

"The pilgrims will be asked to keep in mind the reasons for the pilgrimage and to bring their gifts of love and devotion to Christ to share with other pilgrims," Bishop Ingham said.

Other highlights will include a procession of candles carried by student leaders of the diocese's Catholic schools and a replica of the World Youth Day cross.

A special brass plaque honouring the life of World Youth Day founder, the late Pope John Paul II, will be blessed.

"The original plaque was made for the Vatican but a replica has been donated to the diocese by Mr Warwick Hanson of Anglicare. It's going to be blessed and will hang in the cathedral," Bishop Ingham said.

Doors to the entertainment centre will open at 5pm when music will be provided by a 100-piece WYD band and choir, followed by the Mass from 6pm.

"The choir of young people from throughout the Wollongong diocese has been practising for months under Angela Quinn from Kiama, who is dynamic," Bishop Ingham said.

The first WYD was held in Rome in 1984, and continues to be held every three years. The Sydney event will represent Bishop Ingham's third, after he attended Toronto in 2002 and Cologne in 2005.

Another highlight of today's "Days in the Diocese" program will be an Everything Aussie Festival in beachside Lang Park from 12.30pm featuring a full program of activities including amusement rides, sideshows, international and Australian food and live entertainment.

The "Wollongong Olympics" will begin at 3.30pm, featuring 11 international youth teams pitted against an Australian side in such events as volleyball and relay races.