Hi hi. Simply visit this link after you've bought the bundle, then download all plugins. Actually when you've bought the bundle, you can visit any plugin page on my itch.io, then you'll see they're all free to download.
If you visited a plugin page, clicked on Download but if it didn't download, it could be due to Internet connection. At the moment I'm writing this, I'm also experiencing low connection speed to itch.io (can't be due to my internet). Do try again later and see if it works.
