Integrating Okta into Asp.Net Webforms without Startup.cs

I’m attempting to integrate an Okta hosted login into some Asp.Net Webforms applications, however none of these applicaitons have a Startup.cs file. I’ve been working off the example here, but the configuration is shown using a Startup.cs fille.

I believe I need to use the global.asax file to set it up, something like this:

But I’m not sure how to actually apply these options in the Global.asax since there is no IAppBuilder app variable.

Any instructions on how to set this up inside a Global.axap would be helpful.