Improve documentation - add notice about public key

documentation/v0.2.0/getting-started.md

@@ -244,7 +244,19 @@ $ ssh-keygen -t rsa -b 2048
 $ ssh-keygen -p -f <filename> -m pem
 ```
 
-Then copy content from generated file.
+Then copy content from generated file. 
+
+#### Public key
+
+If you want to upload your public key to your Git server you need to extract it.
+
+If key was generated by `openssl` then you need to type this to extract public key:
+
+```bash
+$ openssl rsa -in <filename> -pubout > <filename>.pub
+```
+
+If key was generated by `ssh-keygen` the public key content is located in <filename>.pub and there is no need to extract public key
 
 #### Configure SSH authentication