IMPORTANT: Rainmeter uses gdi+, so unless you are running WindowsXP you need to download the gdiplus.dll from here (just put the dll into the same folder where Rainmeter is or into Litestep's folder if you're not running Rainmeter as standalone).

Installing for Explorer

Get the installer version of Rainmeter from http://www.rainmeter.net) and run it. If you dislike installers, you can also get the zipped archive and uncompress it to some folder. Rainmeter is ready to be used after that. Note that if you want that Rainmeter starts with the Windows you need to keep the "Startup folder"-option checked in the installation.

Installing for Litestep

To install just copy everything from the zip-file to a Rainmeter-subfolder in your Litestep-folder (i.e. wherever $litestepdir$ variable points to. Usually C:\Litestep\). You don't need the Rainmeter.exe if you are using Rainmeter as Litestep plugin, but there is no harm keeping that also in the folder.

After copying, open your step.rc and add following line:

LoadModule $litestepdir$Rainmeter\Rainmeter.dll

... and recycle. Most of the configuration of Rainmeter is done in a Rainmeter.ini file and not in the step.rc. Check the Settings-section for details.

Uninstalling

If you installed Rainmeter with the installer you can uninstall it from the "Add or Remove Programs". Otherwise just delete all the files you uncompressed from the zip-file (make sure that Rainmeter isn't running when doing that).