It is strongly recommended to do a little bit of research before jumping feet first into modding. There are some hidden features that affect how you mod your games. Several things about the tool may be unintuitive. Starting out with MO2 can be a bit intimidating. The installer can still be used to create a portable installation of MO2. The installer version is usually preferred for ease of installation.
MO2 can be downloaded from GitHub or Nexus Mods. It is now actively maintained by a team of developers, from all backgrounds, and is now able to do much more than Tannin ever envisioned.
MO2 was initially started by Tannin, the creator of the original Mod Organizer, to take care of 64-bit games such as Fallout 4.