Setting up a new user account is a bit of a tricky one, but shouldn't be too hard.
First of all, Resolume Avenue is installed in the Applications folder of your computer. It is accessible by all users of that computer on the same license. So no problems there.
'Old' compositions and source files created by other users can be opened and used. You have to keep an eye on the users access level and where the compositions and source files are saved though. By default, Avenue compositions are saved in the Documents folder of the current user ([yourhomefolder]->Documents->Resolume Avenue 3->compositions). This folder cannot be accessed by other users.
If you manually copy it into the new users Documents folder (by setting the permissions or using the shared folder), the new user will be able to open the composition. Note that any files that are stored in a location not accessible to the new user will not be loaded. By using an external harddrive to store your footage (which is recommended anyway), you won't have to worry about this.
Hope that clears things up a bit.
PS Remember the words of the mighty MCP: 'He's not any kind of program, Sark. He's a user'