All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
You have not clarified the content of the papers and whether such inscriptions contain supplications and Quranic verses or whether they are talismans (written in a language that is not understandable) and contain words of disbelief. At any rate, you should know that the door of repentance is open and will not close until the sun rises from the west. Allaah The Exalted urged repentance, saying (what means): {Say, "O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allaah. Indeed, Allaah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful."} [Quran 39:53] He also said (what means): {And it is He who accepts repentance from his servants and pardons misdeeds, and He knows what you do.} [Quran 42:25]
As for how to repent, it is sufficient for you to regret committing that sin and resolve never to do it again.
Please refer to Fatwa 83434 about the ruling on amulets and Fatwa 86527 about the conditions for sincere repentance.
Allaah Knows best.