fix: correct instructions in Readme

Author: sanjayankur31

README.md

@@ -38,13 +38,13 @@ If you installed the NeuroML_API in a non-standard location, you may need
 to set the `CMAKE_PREFIX_PATH` CMake variable to that location in order to
 find the package.
 
-## Building the API yourself
+## Building the API
 
-The NeuroML API is built using CMake, and the process works best with
-'out of source' builds, where you build the API in a folder separate
-from the source tree. Having cloned the repository, we therefore suggest
-you create a separate 'NeuroML_API_build' folder adjacent to the source,
-change into it, and then run the build configuration commands:
+The NeuroML API is built using CMake (versions >= 3.14), and the process works
+best with 'out of source' builds, where you build the API in a folder separate
+from the source tree. Having cloned the repository, we therefore suggest you
+create a separate 'NeuroML_API_build' folder adjacent to the source, change
+into it, and then run the build configuration commands:
 
 ```
 mkdir NeuroML_API_build
@@ -62,32 +62,43 @@ You may then run
 * `cpack` to generate an installable package (see [cpack documentation](https://cmake.org/cmake/help/latest/manual/cpack.1.html)).
 
 The default CMake options should be appropriate for most cases. The only
-essential external dependency is [Xerces C++](http://xerces.apache.org/xerces-c/) which should be found
-automatically if installed.
+essential external dependencies are [Xerces
+C++](http://xerces.apache.org/xerces-c/) and [CodeSynthesis
+XSD](https://www.codesynthesis.com/products/xsd/).
+
+On Ubuntu based systems, you can install Xerces and xsd from the standard
+repositories using `apt`:
+
+```
+sudo apt-get install xsdcxx libxerces-c-dev
+```
+
+On Fedora and other RPM based distributions, you can install Xerces and xsd
+from the standard repositories using `dnf` or `yum`:
+
+```
+sudo dnf install xsd xerces-c-devel
+```
+
+If you install xsd in a non-standard location, please set the `XSD_ROOT`
+_environment_ variable to the root folder for the software (i.e. the folder
+containing `bin` and `libxsd` folders).
 
 You may wish to change the `CMAKE_INSTALL_PREFIX` to specify where the API
 will be installed. The generated library will be placed in a `lib` subfolder,
 and all necessary headers in an `include/neuroml` subfolder.
 
 If you wish to regenerate the C++ bindings (because you have changed the
-XML Schema or xsdcxx options) you will need [CodeSynthesis XSD](https://www.codesynthesis.com/products/xsd/) installed on
-your system and findable by CMake. The build will search standard install
-locations, but you can also set the `XSD_ROOT` _environment_ variable to the
-root folder for the software (i.e. the folder containing `bin` and `libxsd`
-folders). You can also change the schema file to use by setting the variable
-`NeuroML_SCHEMA_PATH` in CMake.
-
-On Ubuntu based systems, you can install xsd using `apt`:
+XML Schema or xsdcxx options) you will need to pass `REGENERATE_BINDINGS=ON` to
+the CMake command:
 
 ```
-sudo apt-get install xsdcxx
+cmake -DREGENERATE_BINDINGS=ON ...
 ```
 
-On Fedora and other RPM based distributions, you can install xsd using `dnf` or `yum`:
+You can also change the path to the schema file to use by setting the variable
+`NeuroML_SCHEMA_PATH` in CMake.
 
-```
-sudo dnf install xsd
-```
 Once the bindings have been regenerated, you can run `make copy_wrappers`
 to copy the new versions back into the source tree, for committing to the
 repository.