This is a utility written specifically for OpenMW users who want to use lots of mods, and don't want to wrestle with using MW Classic tools to merge their leveled lists.
First, make sure you have python (version 3.3 or higher) installed on your system and reachable.
Second, make sure the script itself (omwllf.py) is downloaded and available. You can download it from github at https://github.com/jmelesky/omwllf
Then, install your mods in the OpenMW way, adding data lines to your openmw.cfg.
Make sure to start the launcher and enable all the appropriate .esm, .esp, and .omwaddon files. Drag them around to the appropriate load order.
Then, run omwllf.py from a command line (Terminal in OS X, Command Prompt in Windows, etc). This should create a new .omwaddon module, and give you instructions on how to enable it.
Open the Launcher, drag the new module to the bottom (it should be loaded last), and enable it.
Finally, start OpenMW with your new, merged leveled lists.
Having everything automatic is darn handy, but some of us have multiple config files and setups. OpenMW can handle that, so omwllf should be able to, too.
There are some useful command-line arguments:
-c (or --configfile), which allows you to specify a specific config file to use-d (or --moddir), where you can set the directory in which to put the new mod-m (or --modname), which lets you set the name of the new mod (I like the default of OMW Mod - <today's date>.omwaddon, but to each their own)All of those are optional (obviously), but when you need them, you need them.
Are you having a problem? I can only fix it if I know about it. You can file an issue on the github project. I'm also trying to be available on the OpenMW General Discussion forum, and sometimes on the #openmw irc channel.