added note with SSH Key instructions

Author: NickIliev

README.md

@@ -585,7 +585,6 @@ To learn how to suggest a new feature or improvement, click [here](https://githu
 To learn how to contribute to the code base, click [here](https://github.com/NativeScript/nativescript-cli/blob/master/CONTRIBUTING.md#contribute-to-the-code-base).
 
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-
 How to Build
 ===
 ```
@@ -599,6 +598,10 @@ grunt
 To use the locally built CLI instead `tns` you can call `PATH_TO_CLI_FOLDER/bin/tns`. For example:
 `PATH_TO_CLI_FOLDER/bin/tns run ios|android`
 
+> NOTE: You should have [SSH key set](https://github.com/settings/keys) for your Git in order add the submodule via [smart git protocol](https://github.com/settings/keys).
+Instruction on how to set new SSH key in Windows, Mac and Linux can be found [here](https://help.github.com/articles/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent/#platform-windows).
+If you try to clone without SSH key setup, you will receive error _"Permission denied (publickey). Please make sure you have the correct access rights"_.
+
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 License