Currently there are ready-made daily images done for N900 in
Note these images has no pre-testing before public so they can be more or less broken. There is however also ready-made weekly builds available.
Kickstart files are stored in gitorious repository http://meego.gitorious.org/meego-os-base/image-configurations
From these repos you can find N900 specific kickstarts from core and handset directories.
Follow the instructions in Creating image using MeeGo Image Creator to create the raw image with mic-image-creator. For Nokia N900, you want to make an SD card install so you should create a 'raw' image.
To use the created image see MMC Installation for howto write the image and start it up.