The OmegaT web site contains links to various OmegaT resources, so you should probably start there. User support is provided at the OmegaT Yahoo User Group. The archives are searchable even without joining the group. New versions of OmegaT can be downloaded from OmegaT SourceForge.net Project, where you may also file bug reports and requests for enhancements.
Remember though, every good bug report needs exactly three things:
More in Painless Bug Tracking article by Joel Spolsky
You should add copies of files, portions of the log, screen shots, anything that you think will help the developers to find and fix your bug. Note that bug reports and requests for enhancements are publicly visible, so you should not add any sensitive files. If you want to keep track of what is happening to the report you should register as a SourceForge user, login and file a bug report being logged in, or simply click Monitor on top of the report.
To contribute to OmegaT, first join the user group (via web or by sending an email to OmegaT-subscribe@yahoogroups.com). You can join the developer group - via web or by sending an email to omegat-development-request@lists.sourceforge.net with subject "subscribe" - if you would like to get involved in the OmegaT development,.
To translate OmegaT's user interface, user manual or other related documents, first read Localizing and customizing OmegaT guide, and join the OmegaT translators' group (via web or by sending an email to omegat-development-request@lists.sourceforge.net with subject "subscribe").
And get a feel of what is going on in the OmegaT world...