Add Installing

Installing.md

@@ -0,0 +1,24 @@
+Use GIT to clone this repo or download the latest Version ZIP file from Releases and unzip to your PC.
+
+It is important that you have Python3.11 and Pip installed.
+
+In the folder you unzipped to, create an environment
+
+## On Windows
+```
+python -m venv venv
+source venv\Scripts\activate
+pip install .
+```
+
+## On Linux/MacOS
+```
+python -m venv venv
+source venv/bin/activate
+pip install .
+```
+
+## Run the app
+```
+ink-calc
+```