To get from github: https://github.com/HL7/fhir-mCODE-ig
https://build.fhir.org/ig/HL7/fhir-shorthand/overview.html A nice look into the general nature of FHIR shorthand, with links to the best next places to go for more information
https://fshschool.org/docs/sushi/project/ A good tutorial site. The page given explains creating about the simplest possible project using FSH and how to generate the about the simplest possible FHIR Implementation Guide from it, using the standard FHIR Implementation Guide Publisher software. Other pages on the site cover how to set yourself up with the basic software for using FSH, including the language processor Sushi (with apologies for all the fish-related puns), and GoFSH, which to some degree reverse engineers an existing IG (like, say, the PoCD on) into FHIR Shorthand (.fsh files) source code.
Some working documents for the DeviceAlert project:
Draft DeviceAlert rationale mockupDoF Alerting