The linked install instructions are only for Tequila and other legacy / non supported launchers. There are no more "Install instructions" for HCLauncher, other than to run it and select your base path as it tells you to do in the program. The asset path is automatically added to the HCLauncher for all active profiles when the program runs.
Again I'm SUPER confused on what exactly @Slayde is trying to do. As in the quoted post, you don't need to search for any mods to download the installer, the big blue "Download" buttons for Windows / Mac *ARE* the Mod Installer. Click the applicable one, unzip it, run the program inside and tell it where your BASE install is, if you don't know where it is. Open HCLauncher, click the Gear, and the install location is right there.