If you have a notebook and want to convert it to a package:

1. Wrap the notebook code between BeginPackage["context`"] and EndPackage[]. Make all the input cells to be initialization cells.

2. Save the .nb file as a .wl file in a place where MMA will find it. Filename same as the context. PackageTest in this example.

3. It should now be possible to call and use the package

The context mark is in my code and in the message. However, the post eliminated the hash marks in the second paragraph. Thanks for pointing that out. I'll try to fix the post.