Setup instructions unclear and out of date

Thank you so much for creating an issue. Yes, Xero has changed their terminology over the past few years.

I think the instructions on the Xero Configuration form are up-to-date, if that helps you in the short term to get started. You should be able to visit or https://developer.xero.com/app/manage after logging into Xero. And "Web App" is the equivalent of a private application in the options.

1. Install xero module.
2. Visit the the Xero Configuration page from Administration > Configuration > Web Services
3. Copy the pre-filled value in the "OAuth 2.0 redirect URI" textfield.
4. Follow the link labeled "Xero's Developer Portal" in a new window or tab. Log into Xero.
5. Choose Web App and paste in the Redirect API for the Xero app.
6. Copy the Client ID and Secret back into your site’s Xero Configuration page.
7. Press the Save button
8. Press the Authorize button to grant the site access to the Xero application.

I hope this helps.

I linked to the project repository page on GitLab on the drupal.org project page. That page renders the README.md file and contains the same steps above, but more detailed.

I updated the project page with the newer terminology.

Let me know of any additional questions that need to be answered to clarify usage. I think that it may need to link to some contrib. modules that make use of Xero API or link to the xero_example module.

Thanks very much for your speedy reply. I did manage to work out those steps myself, but I found I was still having lots of problems (with commerce_xero), and it wasn't clear to me whether this was because I had not completed *all* the necessary Xero API setup steps. I'll report the other problems separately.