Security in BO

Hello,

Has anybody a manual of authorization and access level?

I want to organize security for objects, but don't understand some features.

If somedy can show how I can organize security in BO look like BW(users and roles) it'll be great.

I transfered roles and users from BW and create new users in BO.

But I don't understand what's a Principal, why all users member of Everyone group, who assign folder to user or folder e.t.c

So maybe somebody knows:

Is it possible to set access that user can edit some report and save it to folder/another folderand at this time another user can only read objects?