Subdomain takeover

Is it possible thar we can take over any vulnerable subdomain using fastly service or need to signup server which server that subdomain use
Or do work with fastly i search on github and read alot but little bit confuse. About that

I noticed that Fastly doesn’t allow you to use some subdomain if the top domain or another subdomain is already being used by other customer. For instance, let’s say that I added to a Fastly service, when you try to add to a Fastly service you are going to get an error telling you that someone else is using that domain.

Yeah you correct and if domain is added so it mean we can takeover or vulnerable subdomain

And tell me if i use aws s3 bucket so i able to takeover any vulnerable subdomain

And 2nd question is that how i register vulnerable subdomain in github
I try buy git hub ask for cname
So how i added cname from where i get cname record

As I said, it depends on the domain already being used by someone else on Fastly or not.

S3 is easier to take over as long as the subdomain is pointing to an non existing bucket.

I never found a subdomain pointing to a non existing Github page. But you can find all your answers about how to configure a github page and adding a CNAME on