1. Download a CVS Plugin
To enable CVS within Codewarrior, you have to install a small (free) plugin. You have two different offerings:
mwCVS developed by Metrowerks and available on their web site
abCVS developed by Alberto Barbati and available there
I cannot tell whether there is some big differences between the two plugins. The main difference concern the configuration panel where you define your CVS settings. I just found mwCVS simpler to use as you just need to provice your CVSROOT string and a password to connect. The rest of the article focus then on this plugins. Detailed instructions concerning abCVS are available from its homepage.
The mwCVS archive shall contain at least the following files:
mwCvs.dll,
pMwCvs.dll,
cvs.exe,
cwspawn.exe.
2. Install mwCVS
Locate your Codewarrior installation. By default, this should be something like
C:\Program Files\Metrowerks\CodeWarrior for Symbian Pro v2.5
This of course depends of your version and how you installed it. From this installation directory, copy:
mwCvs.dll in .\Bin\Plugins\Version_Control,
pMwCvs.dll in .\Bin\Plugins\Preference_Panel,
cvs.exe and cwspan.exe in .\(Helper Apps)
Start or restart your IDE so that the new plugin is now recognized.
3. Configure the CVS access
By default, the Version Control feature is not enabled in Codewarrior. You can decide to turn it on globally (i.e. for all future projects) or on a per project basis. The procedure is the same in both case. The only difference is:
if no project is open when you edit the version control settings, then the IDE apply the changes globally.
if a project is active when you edit the version control setting, then the change are only applied to this project.
To activate CVS version control, select Edit and Version Control Settings..., this should open the following window:

Check the Use Version Control button
Select mwCVS in the Method drop-down list
Check the Use global setting as default button to enable CVS for all your project.
Don't bother about the Login Settings. You won't be able to change them using this screen.
Select the mwCVS tab located on the left, gives you access to a few extra options :

Uncheck the Compatible with WinCVS 1.2 button if you don't use WinCVS 1.2 (the v1.3 is out now and is fully compatible with he mwCVS plugin).
Finally, Apply to save your change.
Next
Using mwCVS with a secure shell:
1. Download and install Pageant and PLink from the PuTTY Download Page.(http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html)
2. Run Pageant and add your SSH key(s).
3. Create a new environment variable called CVS_RSH, with a value C:\path_to_plink\plink.exe. (My Computer/Properties/Advanced/Environment Variables/New)
4. Run CodeWarrior and turn on Version Control, as described in the article.
5. The value of the CVSROOT variable should begin with :ext: eg. :ext:your_username@your.cvs.host:/your_cvs_root
Note: Do NOT try to explicitly login with this method as described in the article, it is not supported by CVS. Instead, CVS logs in for you every time it is required.
6. Enjoy!