You can add multiple users in your project (provided you have access to do that).
For the using Redmine, you need to have a Redmine account.Once You have Redmine account and you have logged in to it, you will find it useful for your project.Next step is that you should create a new project or if project is already created by another person, tell that person to add you in that project.Once you are ready with the project and permissions to access that project, you can start tracking issues and using Redmine effectively.
Redmine is a project tracking tool and it can be used for all project/issue tracking.
