Update README

README.md

@@ -212,9 +212,14 @@ of fixing it later, which will make me eternally grateful.
 
 NITF Library Users: General Issues
 ----------------------------------
-If you want to use the default TRE plugins that come with the library,
-NITRO already knows where they are installed, and you don't have to
-do anything.
-
-If you want to override this behavior, you can set the
-`NITF_PLUGIN_PATH` environment variable to your preferred location.
+NITRO handles TREs by loading dynamic libraries at runtime. Therefore, you need
+to make sure NITRO can find them.
+
+    - If you are building from source, the location will be compiled in, and
+      you don't have to do anything extra.
+    - If you are working from a binary release, you will have to tell
+      NITRO where the plugins are by setting the `NITF_PLUGIN_PATH`
+      enviornment variable.
+      This should look something like `<install>/share/nitf/plugins`.
+    - If you wish to use a custom TRE location, you can also specify that
+      with `NITF_PLUGIN_PATH`.