Make sure to first have SuperBLT, and BeardLib installed. Click the links in the dependency list.

Optional video tutorial for installing SuperBLT, BeardLib, and mod_overrides mods: https://youtu.be/rin_sjSJIkg

1. After downloading the mod, use a program such as 7zip or WinRAR to extract the main folder of the mod.
2. Drop that folder into the mods folder which is supposed to be in the game's installation folder (don't know where that is? click here)

To install third-party addons:
Base Addons are included and installed automatically as part of Minimalist HUD Ultimate! You do not need to change these folders in the Base Addons folder at all, unless you wish to remove some to free up disk space.

First, make sure you have followed the instructions above to install the main Minimalist HUD Ultimate mod.
Then, download the addon(s) you want to install.
Unpack them if they are archived (such as in .zip or .7z format).
Place the addon's folder into the folder at /PAYDAY 2/mods/saves/MHUDU Addons/.
If it is installed correctly, it should show up in the mod options menu, under Minimalist HUD Ultimate's Addons menu.
You can also check the BLT log for relevant debug information, in your mods/logs/ folder.
(There aren't any besides the ones that MHUDU comes with right now, so this probably won't be relevant for some time, if ever.)