Hi, the boost section will show available perks, like disney (but not limited to). Often, there are offers for youtube plus and a few others.
In regards to the disney, it should have a button under the offer labelled redeem or similar. Once you click that, it will be replaced with your code.
You're free to navigate the boost section to see what's available. Just be a bit careful when it comes to the claim buttons as they seem to impact your original expiry times.
All the best!