diff --git a/Developer's-Guide.md b/Developer's-Guide.md
index 9eed69f..c128f3a 100644
--- a/Developer's-Guide.md
+++ b/Developer's-Guide.md
@@ -62,12 +62,18 @@ If you're using PyCharm, you can configure the project to use your virtualenv in
 ## Running from sources
 
 ### Windows terminal (using git-bash)
+If you run from sources for the first time, you need to build the frontend, otherwise you won't be able to see the map. For the frontend to build, you need npm installed, which you can get on the [Node.js webpage](https://nodejs.org/en/download/). After installing node.js and npm, do the following for the first build:
+```
+cd client
+npm install
+npm run build
+```
 
 Every time you update the repo you should rebuild the front-end:
 
 ```
 cd client
-npm build
+npm run build
 ```
 
 If you're not developing the front-end (or the API boundary) that's enough. Otherwise, see `client/README.md`.