PARCC’s Betty HPC Cluster is open to all members of the Penn community. Anybody can go to https://parcc.upenn.edu/training/faculty-info/coldfront/ to set up an account and initial project. In order to actually use the resources, an account must have at least one valid project backed by a valid budget code for any costs incurred.
For more details, PARCC’s main website is https://parcc.upenn.edu/, and their support intake page can be found here: https://parcc.upenn.edu/support/.
If you are a researcher working with a PI, they can directly request access for you under one or more appropriate projects, again using the ColdFront console linked above.