README.md: add usage instructions

README.md

@@ -6,3 +6,31 @@ and it also shifts every time there is a long weekend or other break.
 calendar-tool takes all these disruptions into account over the course of the year.
 
 Takes a YAML configuration file, and saves the calendar as ICS, to be imported in Google Calendar or other calendars that can support it.
+
+## usage
+
+- Clone repo:
+    ```
+    git clone https://github.com/dogeystamp/calendar-tool
+    cd calendar-tool
+    ```
+
+- Copy `config.example.yml` to `config.yml`:
+    ```
+    cp config.example.yml config.yml
+    ```
+
+- Edit the configuration (the comments and examples should explain everything):
+    ```
+    vim config.yml
+    ```
+
+- Run the script:
+    ```
+    python -m venv venv
+    source venv/bin/activate
+    pip install -r requirements.txt
+    python3 main.py
+    ```
+
+- Your calendar should now be in `cal.ics`.