(I am newbie to tortoise SVN)
I have 2 folders in my tortoise SVN. Each need a different set of authorization (I do not want people who have access to the first folder to have read / write access to the second folder).
How can I accomplish it? I noticed that all permissions are defined in a file in the root level.
This is covered in the Subversion Book section on Path Based Authorization. You can check out the link for more details, but I would just draw your attention to this part:
A lot of administrators setting up Subversion for the first time tend to jump into path-based access control without giving it a lot of thought. The administrator usually knows which teams of people are working on which projects, so it's easy to jump in and grant certain teams access to certain directories and not others. It seems like a natural thing, and it appeases the administrator's desire to maintain tight control of the repository.
Note, though, that there are often invisible (and visible!) costs associated with this feature. In the visible category, the server needs to do a lot more work to ensure that the user has the right to read or write each specific path; in certain situations, there's very noticeable performance loss. In the invisible category, consider the culture you're creating. Most of the time, while certain users shouldn't be committing changes to certain parts of the repository, that social contract doesn't need to be technologically enforced. Teams can sometimes spontaneously collaborate with each other; someone may want to help someone else out by committing to an area she doesn't normally work on. By preventing this sort of thing at the server level, you're setting up barriers to unexpected collaboration. You're also creating a bunch of rules that need to be maintained as projects develop, new users are added, and so on. It's a bunch of extra work to maintain.
Just to round the post of codeka up. You can't set (at least I never have found out how) any permissions for the repo in tortoise as it is the SVN client application. You would have to set the permission on your svn server. If you happen to be running VisualSVN Server (free) you can setup user rights in a windows-easy manner (point and click).