How should repentance be for a person who circulates prohibited video clips and pictures

I used to watch prohibited video clips and pictures and then share it with my friends and circulate it on a massive scale. I have repented from all of that, but what do I do about the video clips and pictures which I shared with people in the past?

First of all, you watching those images makes you sinful, but then to share it and circulate it is even worse. This is because you will share the sin of those who watched it because of you. However, if you have repented, the person who repents is like a person who has not committed any sin. These bad deeds will be converted to good deeds like Allaah says,

(إِلَّا مَن تَابَ وَءَامَنَ وَعَمِلَ عَمَلٗا صَٰلِحٗا فَأُوْلَٰٓئِكَ يُبَدِّلُ ٱللَّهُ سَيِّـَٔاتِهِمۡ حَسَنَٰتٖۗ)
… except for those who repent, believe and do righteous work. For them Allaah will replace their evil deeds with good.” (Al-Furqaan 70)

Sinful things which are shared with other people must be declared as such to the people with whom you shared it and misled, as should the fact that you have repented to Allaah. You are embarrassed for anyone who will see it after this, and you are free from this responsibility. You should request them to delete it from their devices. Beyond that, you cannot force people to do anything. Hence, making this declaration is enough.