As suggested by @030, I have prepared two screenshots that show how to connect the .yml files with the build pipeline. 

 1. Rename the .xml file in the repository

 2. Open the pipeline editor
[![Pipeline editor][1]][1]

 3. Select the file from the dropdown
[![enter image description here][2]][2]

 4. Rename it and click on `save`.

After the existing .yml is assigned, the pipeline works as before the renaming.

  [1]: https://i.sstatic.net/KJX7y.png
  [2]: https://i.sstatic.net/4iStF.png