Copy the editor folder from FCKeditor distribution into SharpWebMail\asp.net\fcke folder. _source and filemanager subfolders aren't needed so you can delete them.
Windows only instructions:
Copy SharpMimeTools.dll into sharpwebmail\bin\net folder (if it doesn't exist create it)
Copy log4net.dll into sharpwebmail\bin\net
Copy FredCK.FCKeditorV2.dll into sharpwebmail\bin\net
Copy DotNetOpenMail.dll into sharpwebmail\bin\net
Copy OpenSmtp.dll into sharpwebmail\bin\net
Then open sharpwebmail\SharpWebMail.sln combine file with SharpDevelop 2.x
In SharpWebMail/asp.net folder are the new built files.
Nightly builds
The last SVN code is automatically build everyday at 0:00 UTC. If there has been SVN activity, you'll be able to download them from 'SharpWebMail daily builds'.
Contributions: Patches, bugfixes, translations, suggestions, etc.
There is much work to be done in SharpWebMail and all sorts of contribution are welcome. The main development areas now are:
XHTML interface.
Full IMAP support.
More translations.
Provide and easy framework to extend/change functionality.
Intensively test everything.
Those are the areas where I'll focus my development cycles. If you want to help in those or other things more important for your environment, you are welcome to contribute to the project.
If you want to contribute a new translation click here for detailed instructions.