Currently the most common hardware is 64 bits architectures PC — Intel / AMD — also know as x86_64.
Choosing another architecture certainly means that you already know what you are doing.
Please read also:
OMLx 4.3 Release Notes
OMLx 4.3 Errata
Select the release in the list, it should automatically open a download page from a mirror nearby your location.
Click on the desired version to open the details, and download torrent or iso file from the links in the right panel.
We also seed the latest releases from own seedbox to guarantee a quick downloads. Previous release downloads may be slower depending on archive.org and other remaining peer seeders.