Modding
Sim Settlements is a Video Game Mod specifically created for Fallout 4 as are the official Expansion packs and Community authored Addon Packs.
Modding your video game means that you are "making changes" to your video games files. While the benefits are great, there is a responsibility on you to learn "how" to mod your video game properly. This means gaining an understanding from the "technical" point of view as well as learning how to use the "tools" the Modding community at large have created to help you.
The Sim Settlements community has put together some guides and tutorials to help you better understand the details and tools that allow you to apply Mods to your video game.
Please note: these are works in progress.
PC Modding
These links will take you to the Forum.
PC Help Page _ Basic Guide and Links
XBOX Modding
These links will take you to the Forum.