You must deploy your workflow. In the Enterprise edition you can do this from the console. In community (or Enterprise) if you set redeploy to true in your workflow context file it will deploy automatically on restart. However, be careful of this latter mechanic, you need to restart Alfresco once with redeploy set to true and then change redeploy to false so that the workflow will not be redeployed again and again at boot time. Of itself, this multiple redeployment isn't harmful but you end up with masses of versions of essentially the same workflow.
Good luck
Bob Johnson