Arm processor based HPC platforms are now available. In the UK there is Isambard (Cray XC50) and three Catalyst (HPE Apollo 70) systems. These systems are supported by Arm’s extensive HPC ecosystem, which means that most applications will build with little or no modification, furthermore it usually takes little effort to achieve maximum performance out of your application on Arm. The main objective of this walkthrough is to demonstrate how easy it is to use Arm HPC systems to do real science. The session will begin with an overview of Arm in HPC, Isambard and Catalyst. Then, a more in-depth demonstration of some of the tools that are available. This will include compilers, numerical libraries, debugging tools and profiling tools. The demonstration will end with a discussion of some recent results from Isambard and Catalyst. Throughout the walkthrough there will be opportunity to discuss how to get best performance with your application or to use the tools, and to ask any questions in general about Arm in HPC.