How to get access to and download data from dbGap

I'd like us to document how to get permission to access dbGap data, and then how to go about downloading it, as this is not a straightforward process. In the future (but low priority), it would be useful to investigate where to analyze sensitive data that must be kept private (e.g. WGS from patient cohorts) though we currently don't have any such data, so are off the hook for now.