That sounds more like a question about how to use Tasker, not how to use the Beeminder API, which is sort of out of the scope of what I was focused on getting working. I recommend you read up on how Tasker works and how to use it.
But generally, unless the app you are using has a Tasker integration, you are fairly limited in how you can get data from another app and use it in Tasker. If you can be more specific about what you’re trying to do I can probably help though.