How to make copied DLL's work?

[Tauven]

Hi i've made some changes in few DLL's to make my own items and shops fully work as intended but all made in the origional DLL files.. when i make a copy of those and make same changes it doesnt work (the game doesnt use the copy just origional ones without any changes)

So how do i make the copied ones override the origional ones?

The ones i did changes in was the two DLL's TaleWorlds.Core and TaleWorlds.CampaignSystem

//Tauven