Ah, that’s a different issue.
The project is on Github as you know. You need to run git clone https://github.com/rancher/external-dns on your own computer (that command line is generic, it might be different if you’re not on Linux). That will check out the source code to your system in a directory named external-dns in the directory where you executed that command. You will have to rearrange things and rename things as I mention above because of how Go works.
Good luck!