Steps to get started with NFIRS:
The first thing you should do is contact the point of contact for your state. NFIRS (although it is national) is typically coordinated at the the state (or district) level and state coordinators can help you get started.
eNFIRS is the new website from FEMA. eNFIRS is the new (2020) and modern web-based interface into the NFIRS. Volunteer Fire Department administrators, coordinators and firefighters can log in and enter incidents, run reports and more. Check out the eNFIRS training created by U.S. Fire Administration. Here is an example training video:
Using the NFIRS system requires knowledge of fire response and terminology but also knowledge of NFIRS 5.0 codes and coding. Two of the larger lists are Incident Type and Actions Taken. You can use the reference guide (see link below) however you can also create an Incident Type / Actions Taken cheat sheet of common codes before you start entering codes.
NFIRS codes (numeric values for a concept) are pretty consistently organized with groups, and sub-groups. When coding an element determine the group you are looking for, then select the best fit within that group.