I have a windows application getting ported for Mac.In windows i store encrypted data in the registry.But when it comes to Mac im unfamiliar.
The application is licensed per PC.So all Users using the Machine will be able to use it.So in windows im storing the key in HKEY\LOCAL MACHINE
How does user access rights work in Mac? Where do i need to store the data?
This type of data is usually stored in a file in Application Support directory. If you want to store one file for all users you should choose /Library/Application Support system directory.
The directory is not user-writable, so you will have to run installer with root privileges. This directory can't be used by sandboxed apps.
You should create a subfolder in this directory and store your file inside.
For more information see The Mac Application Environment, especially Table 1-1, "Key directories for Mac apps", and File System Basics.
Edit:
Usually OS X apps don't need any installation. They are self-contained bundles that can be run from any location. Usually you keep them in Applications folder (drag it there). System wide /Applications folder is accessible for all users. There is also private ~/Applications folder in each user's home.
On the other hand apps that need to install data to system folders use installers. Installer usually copies application bundle to /Applications folder, but also handles authentication and asks user for admin credentials. Installers may also run scripts.
Maybe your license could be generated by a script during installation?
If not, you would have to generate license file on first application run. In such case, if you want to keep one file for all users in /Library/Application Support, you will have to escalate privileges and ask user for admin access. If you don't want to do that, consider storing separate license file for each user in their home ~/Library/Application Support folder.