Once linked, any piece of inventory listed in your Inventory records can be recorded in the Inventory Used tab of any Incident, Training, or Public Education record.
To make individual items accessible to Inventory Used, open up the item in your Inventory records and change the Linking Type to Incidents/Pub Ed (this also includes Training)
If you'd like to make an entire sub-category of items accessible eg. all Breathing Apparatus, click on the edit list icon to see this list
Highlight the Category/Subcategory, and change the Default Linking type to Linked to Incidents/Pub Ed
Any vehicles linked to Apparatus will automatically be available and don't need to be changed. Apparatus can't be added to this tab for Incidents since they're meant to be listed in the Truck Chart, but can be added to Pub Ed and Training records.
Now that your items are set up, open up an Incident, Training or Pub Ed record and click on the Inventory Used tab.
Click on the add icon which will show a list of category and sub-categories of items that have been made available.
Double-click to add the item to your record and add any comments or cost pertaining to the item.
Item usage can be tracked in the Inventory mod by printing the Equipment Used report.