Its easy, just pick the chan you want, go watch it. With the channel showing up on your TV, you go to DM800 Menu and then REstart/Standby, you enter there and choose, REBOOT.

Then all settings like the channel you were in the volume and other stuff will be saved, when you unplug and plug again the power of the DM it will be there.

Hope you understand

Another comfortable way is to use the Pauli plugin, I believe the plugin is also available in the Newnigma feed.

I think it should be in the feed...
Here is the plugin for manual installation,it works very well with the Newnigma image.

The feed is the Online Plugin Download/Installer (at least for me ;)) and the Online Updater for Enigma 2.
You can easy install the plugin manual:
1)copy the file with a FTP-client to the /tmp directory of your dreambox.
2) go to the Newnigma Software Menu, push the Offline Installerr von /tmp and pick the file and press the OK Button, then its done.

If allready is OK, then you will find the plugin in the extensions menu.