Regarding the 15th station, I've read varying accounts of when and how it was added. Even the Holy See website only lists the 14. Since the Stations of the Cross are a devotional exercise, there are no set rules so to speak just tradition. There are various prayers online but I would think reflecting on what a given station represents and means to you is good- and I'm sure your priest/pastor/minister can suggest prayers.
The Aedicula of the Holy Sepulchre from where Jesus rose from the dead
"And surely I am with you always, to the very end of the ages" (Mt 28,20)