Your Crucible instance must have at least one project, in a fresh install this is imaginatively named "Default Project". It is a good idea to rename this to something more personal. If you plan on having multiple projects, you might also want to change the review key when renaming the Default Project (it defaults to CR), this should not be the same as any other keys (e.g. JIRA project, Bamboo plan) that you use. At Atlassian we prefix our JIRA project keys with CR-, e.g. the FishEye project's key is CR-FE, but you can use whatever you like.
Obviously Crucible projects let you organise your reviews into logical groups, but they serve several other purposes.
- Access control - is set at the project level
- Permission schemes - which roles can do what
- Default participants - e.g. auto add the team lead to every review
- Default length - set the number of week days to set the due date for a new review
You can also associate JIRA issue tracker(s) with your project, by configuring JIRA Integration in Crucible.