The Remote Application Service (RAS) provides a method for any University user to access ISS' PC services, including the software and personal filestore, from their own computer.
To use RAS all you need to do is open your web browser at http://ras.ncl.ac.uk/ and sign in using your campus login details. However, if this is the first time you are attempting to use RAS you will need to install the Citrix Client. Click on the link for Mac Users highlighted below to download the plugin, and ensure you save it locally. Once downloaded you will need to run the installation file to setup the client.

Click Install and the installer should launch automatically, if it doesn't then it can be manually launched from your browser's download folder.
Once you are logged into RAS with the appropriate client installed, you just need to single click on the folders and applications in the Applications Box in order to open them. The applications look and behave just like they're installed locally - they appear as "seamless applications.
If you are unable to install the Citrix Client on the computer you are using then you may be able to use the Java based client.