Question: These kind of error are showing in the 16 files.

When i am going to change then its showing the pop-up 

[![enter image description here](https://i.stack.imgur.com/NM55g.png)](https://i.stack.imgur.com/NM55g.png)

or click on unlock

[![enter image description here](https://i.stack.imgur.com/LDfrV.png)](https://i.stack.imgur.com/LDfrV.png)

My question is this -

How to unlock this file to editing ?

Answer: 
You get the code from git through `Download Zip`. Try `git clone` to download the code.
Like the message box says, find the files in Finder and right click them. Modify their permissions to be writable.