Currently, there isn't a standard between the NFT ecosystem to be able to charge royalties for NFTs sold through different channels.
So, there isn't an option/setup inside the smart contract that will let you charge royalties for future sales of your art.
However, NFTs sold through KoalaMint's mint button will be visible on OpenSea and other marketplaces.
As soon as the first NFT of your collection is sold, your collection will appear under the creator's wallet address on OpenSea.
There, you'll be able to configure royalties for secondary sales made through OpenSea.