Hello, @bruce.mcvicar. Thanks for reaching out.
Please accept my apologies for the delayed reply 
It is super easy, actually.
The first thing you need is to create an account in Bubble (The best way to build web apps without code | Bubble), it is for free.
Then, you just go to the template page you want to purchase, click “buy” (you’ll be redirected to the template’s page on Bubble).
Then click “buy template”, choose the template license you want to buy and that’s all.
You can find the description of the difference between Standard and Developer Licenses, and lot more info on how to get started here:
FAQs - Frequently Asked Questions | Zeroqode
Marketplace Policies | Bubble
When you just have created an app (a blank one or based on the template) your app is automatically getting the Hobby subscription plan. It is free, as you may know, and it is allowing you only to edit/manage your app without running it live (with online traffic, users, etc).
To find out more info on Bubble subscription plans, their differences and usage, please check this page: Pricing | Bubble
First of all, I’d like to suggest you check out a few Bubbe courses to create a common understanding of how the Bubble Editor works and how things are being created using Bubble. This will help you to achieve the necessary skills, for managing, editing, and customizing your Bubble app.
Please take a look:
Lessons | Bubble
Videos | Bubble
https://manual.bubble.io
Courses | Zeroqode Lab
Bubble for Beginners Course | Zeroqode Lab
Second of all, you can try out one of our free templates as a sandbox, for practical experience:
Third of all, when you purchase the template license (Standard/Developer) you are paying only once. The other monthly/annual fees are concerned with the Bubble subscription plan only.
Please let me know if you have any more questions.
Regards,