Modding a mod's data

Hello, I am trying to modify attack, cast, and movement speed in the Grimarillion’s mod
(Grimarillion’s gameengine.dbr → All group → Player Info → Attack/Cast/Movement Speed data)

But I’m not really sure how to “import” grimarillion’s data into the asset manager to change it’s gameengine.dbr.

For posterity, this is done by extracting the contents of the mod files using the ArchiveTool. There’s a guide here: [Tutorial]Use the archive tool to uncompile *.arz and *.arc

Once you’re done you hit Build and you get a new .arz - your new modified Grimarillion mod.