Example for adding Spain translation:

slav0nic@slpc:/tmp$ hg clone https://bitbucket.org/slav0nic/djangobb
destination directory: djangobb
requesting all changes
adding changesets
adding manifests
adding file changes
added 257 changesets with 1613 changes to 916 files
updating to branch default
347 files updated, 0 files merged, 0 files removed, 0 files unresolved
slav0nic@slpc:/tmp$ cd djangobb/djangobb/djangobb_forum/
slav0nic@slpc:/tmp/djangobb/djangobb/djangobb_forum$ django-admin makemessages -l es
processing language es
slav0nic@slpc:/tmp/djangobb/djangobb/djangobb_forum$ ls locale/
es/    fr/    lt/    ru/    zh_CN/ 

After that, go to ​http://www.transifex.com/projects/p/djangobb/ , create translation team or ask access and uploading locale/es/LC_MESSAGES/django.po file.