TheAurumGamer

Hi! I'm relatively new to Forge but have a year of Java under my belt, but I'm stumped by one thing: How do I modify existing blocks and items in the Minecraft game? I already understand the concept of creating new blocks, entities, potions, items, and so forth, but how do i modify an existing block, such as a leaf dropping a slime ball? Help would be appreciated as I have little time to work on this.