To add other projects into Zanata, someone with access to source control (eg a developer) will need to configure the relevant docs projects to enable the zanata-maven-plugin (in pom.xml) and to access the correct server (in zanata.xml).
A Zanata administrator will have to "create" each project which is to be translated, and assign one or more people as project maintainers. (Just ask onjboss-l10n.) Project maintainers can then create project versions (eg 1.0, 1.1). Typically, each branch of the docs project source tree will be linked to its own "project version" in Zanata (via the file zanata.xml in source control).
There are some sample config files, and some useful scripts, here: https://github.com/zanata/zanata/tree/master/client/zanata-maven-plugin/sample-scripts
Once the config files are set up, the source text (.pot), and any existing translations (.po), can be imported into Zanata. In the case of the Weld reference guide, the script zanata_import_all was used for this. (zanata_import_all uses the maven goal zanata:publican-push.)
On a regular basis (eg daily), the script zanata_import_source is used to update Zanata with the latest source text (English). (zanata_import_source uses the maven goal zanata:publican-push.)
There is also a script zanata_draft_build for a draft build of the docs, which pulls the latest translations from Zanata, builds them into documents, but doesn't store them permanently. (zanata_draft_build uses the maven goal zanata:publican-pull.)
At release time zanata_export_translations will be run to pull translations from Zanata, and they will be checked into source control (git). (zanata_export_translations uses the maven goal zanata:publican-pull.)
(The idea is for most of the above scripts to be run by a build server.)
The wiki docs for the Maven plugin are here: http://code.google.com/p/flies/wiki/ZanataMavenIntegration and http://code.google.com/p/flies/wiki/ClientConfiguration.