User level access control for the repositories

Hi Team,

I want to implement the User level access control for the repositories. Please provide me the step by step process to implement in the Bazaar repositories.

Example Scenario:

List of developers can Read/Write to the Development branch code. Lead can only Write (Merge) code from Development Branch to the Main Branch.

Main Branch: Lead can have Read/Write; Developers should not have any permissions.
Development Branch: Lead can have Write/Read; Developers can have Write/Read permissions.

Thanks in advance.

Regards,
Madhu