Add instruction to download Fira Sans Condensed Font to Readme.md

Change-Id: I2a9bab997f150196837e315f16674f4977ba8403
diff --git a/Readme.md b/Readme.md
index ccb1f78..fa787cc 100644
--- a/Readme.md
+++ b/Readme.md
@@ -5,10 +5,15 @@
 The package provides a collection themes for different plotting libraries, following the corporate design of the Leibniz Institute for the German Language (IDS) in Mannheim (Germany).
 
 ## Installation
-```R
-library(devtools)
-install_git("https://korap.ids-mannheim.de/gerrit/IDS-Mannheim/idsThemeR") 
-```
+
+1. Download and install the Fira Sans Condensed font, for example from [Google Fonts](https://fonts.google.com/specimen/Fira+Sans+Condensed?preview.text_type=custom)
+
+2. Install idsThemeR from its gerrit/git repository:
+
+    ```R
+    library(devtools)
+    install_git("https://korap.ids-mannheim.de/gerrit/IDS-Mannheim/idsThemeR")
+    ```
 
 ## Examples
 ### [highcharter](https://cran.r-project.org/package=highcharter) – light with IDS departments palette