...I have already purchased a VPN subscription....
If you have purchased a VPN subscription, the company that you purchased your subscription from should 1) Tell you EXACTLY how to set things up (usually via a Web page with step by step instructions, and 2) If you can't then figure it out, or get it to work, they should offer technical support that will assist you to get things to work. If they don't offer both 1 & 2, above, then you should call your credit card company, cancel payment, and find another service.
But....why do you even feel that you need a VPN? Most folks these days don't need one:
If your only concern is having your communications intercepted by hackers, VPN's are more or less an anachronism that have been made superfluous by current technology:
https://www.nytimes.com/2021/10/06/technology/personaltech/are-vpns-worth-it.html
"The reality is that web security has improved so much in the last few years that VPN services, which charge monthly subscription fees that cost as much as Netflix, offer superfluous protection for most people concerned about privacy, some security researchers said."
Also:
"Many of the most popular VPN services are now also less trustworthy than in the past because they have been bought by larger companies with shady track records." Your commercial VPN may actually be tracking you.