update readme and add requirements.txt

README.md

@@ -4,9 +4,50 @@ Qt SDK Creator - A tool for automatically downloading, building and stripping do
 
 ## Examples
 
-See the ``examples`` folder.  
+See the ``examples`` folder.
+
+## Usage
+
+[Python](https://www.python.org) and [Perl](http://strawberryperl.com) must be installed manually.
+
+The compiler to use must be manually installed prior to using qsc. Currently this means Visual Studio should be installed. `compiler` in the manifest specifies which exact version of VS to use.
+
+Install python packages required for qsc:
+```
+py -m pip install -r requirements.txt
+```
+
+See the [definition of `REPO_BASE_URL` and `REPO_SRC_PATH`](qsc/__init__.py) for where qsc will pull the Qt sources from. You can browse these URLs and discover available versions to place in the manifest `release` tag.
+
+Compose a manifest file describing the build to perform. See [examples folder](examples) for previously-used manifests.
+
+To run the build, point python to the [qsc directory](qsc) as a module:
+```
+py -m qsc manifest.yml
+```
+
+NOTE: For an out-of-tree build, you need to place the qsc repository in the python path. For example:
+```
+set PYTHONPATH=c:\src\qsc
+```
+
+## Resolving "ERROR: Building QtQml requires Python"
+
+If your manifest dictates that QtQml should be built, the build will try to find and execute `python`. This can be problematic as `python` will always exist in the `%PATH%`, but may be a dummy which prompts to install python from the Windows Store (even if you have some other instance of python installed).
+
+To workaround, find your working python install directory:
+```
+py -c "import os,sys; print([x for x in sys.path if os.path.basename(x).startswith('python') and os.path.basename(x).endswith('zip')])"
+```
+
+Then, prefix this to `%PATH%` in your current shell.
+
+For example:
+```
+set PATH=%LOCALAPPDATA%\Programs\Python\Python37;%PATH%
+```
 
 ## License
 
 This program is licensed under the GNU General Public License v3 (or later).  
-See [LICENSE](LICENSE).  
+See [LICENSE](LICENSE).

requirements.txt

@@ -0,0 +1,2 @@
+pyyaml
+requests