Current stable release is OpenMandriva Lx 4.3
OpenMandriva rolling release is "ROME"
1. Download the ISO file
Mirror download (sourceforge.net)
Enter the folders, select the release in the list, it should automatically open a download page from a mirror nearby your location.
Torrent and direct download (archive.org)
OpenMandriva Lx 4.3 archive.org page
Click on the desired version to open the details, and download torrent or iso file from the links in the right panel.
2. Burn it
Transfer the downloaded image to a USB flash drive.
To transfer the live/installation image to an USB storage device you may use:
ROSA-imagewriter, KDE isoimagewriter, SUSE Studio ImageWriter, dd command line.
Please do not use other usb-writing tools as some Windows tools (e.g. Rufus) truncate the volume name and will break the boot process.
3. Try it and install
Reboot your computer and set it to boot from USB. Voila! You have got a fully working OpenMandriva system up. OpenMandriva comes as a live system, so there is no need of installation to try it.
Running OpenMandriva Lx in live mode is useful to know if it works well with your hardware.