Hi Ashu,
It's normally easiest to assign permissions at the folder level. Since permissions inherit by default, using separate folders would allow you to add more reports later, and permissions would be assigned, just by putting them in the right folder.
That being said, assigning permissions for Folders and Reports works the same way.
1. Open the Folder or Report.
2. Go to the Properties Tab.
3. Click Security on the Left Menu.
4. Click "New Role Assignment" (If Permissions are still being inherited, you will need to click "Edit Item Security" first.)
5. Enter the User Name and put them in the Browser Role.
Note: Both users will also need to have Browse Level permissions on the Root Directory, or they won't be able to see the folders that they have permissions on. In my environment, pretty much all Domain Users have Browse Access on the root directory, but
only Folders and Reports that they can use, show up.
Note : If the user is a Local Administrator on the SSRS server. By default they will be able
to see everything.