Here you edit the mappings between a subsystem component and the Interior TRM. The TRM can only be mapped to the subsystem component level, as shown in this diagram. This window has more options than the other Edit Mappings windows, to let agencies enter specifications from their local TRMs into DEAR. When you open this window the first time, the wizard will load the TRM, and it will probably take a lot longer than loading the PRM, BRM, etc., since the TRM has so much more information in it.
Levels 
The Add button is only active at the level of the blue text (technical standards), but you can Find at any level.
Click in the checkbox beside a line to map that line. Do NOT check any DOI-tracked systems unless you know what you are doing; once checked, these cannot be unchecked. To make it easier to find checked lines, no line shows up opened into sublevels unless one of the sublevels is selected. This picture has the sublevels opened only for illustration--since none of them are checked, normally none of them would be opened up.