How long does it take to be granted access to Adobe Stock with a Creative Cloud subscription?
If you have a Creative Cloud subscription that includes Adobe Stock it should be immediate for an individual subscription. I can see by your email address (really not a good practice to make your screen name the same as your email address btw) that you are part of a university so Adobe Stock may not be part of your subscription and you might have to request access from your Creative Cloud administrator at your school. Without further information about the kind of plan you have it can be difficult to answer your question.
Adobe Stock is an optional extra. It doesn't come standard with Creative Cloud.