Yup the Wiki method will work too.
Depending on the route you go FOSS > NE can be as simple as running the installer & having the license handy in /opt/zimbra/conf/
If you use the blog method:
Change platforms (using the exact same ZCS version #)
Then upgrade to NE (run the exact same ZCS version installer but just in NE)
OR
Upgrade to NE (run the exact same ZCS version installer but just in NE)
Then switch platforms (using the exact same ZCS version #)
NOTE:
-The key is using the same zimbra version for the platform change.
-In general, for FOSS > NE upgrades, using the same version is not needed; but if something fails it's a whole lot easier to troubleshoot same version #'s.
-But for the wiki method note that "the network edition server
must be the same release as installed on the open source edition server".
-And of course put on
5.0.6 somewhere in there, either way before or after the upgrade/platform change.
-Be sure to make a backup!
Backup and Restore Articles - Zimbra :: Wiki
I'm kinda guessing you might be changing platforms because there's no NE binary - of course there's plenty of other reasons it could be

If needed, support can assist you with any of the methods outlined in this thread.