Nexus Mods Vortex Mod Manager (I’ll also show you how to install mods manually, but this makes things a lot easier). A few gigs of spare hard drive space for downloading and installing mods.

It’s safe to use and among the most popular mod sites for games, especially Bethesda-made titles. Download and install Vortex. Vortex is a mod manager developed by Nexus Mods.

Vortex can be downloaded here, and then you can grab the Bannerlord support extension. Instructions on how to install them can be found on their respective pages.