How do I access the PDF Suite key?

I just purchased the program for $57 and do not know where to access the key so that I can use the program

Usually you will receive the License Key/ Registration code immediately after purchasing (but it still depends, some company also choose to send keys manually, you should read their policy first).

If they promised you will receive the keys instantly, then, most of the time, your email has caught the "License Key Email" as spam, just go check your Spam/Junk Mail folder to see if there's an email contains the key.