Buy more storage on web

I’m using a friends phone to sign on to my iCloud using their browser. I am trying to access my email but my storage is full, and it says I need to upgrade to buy more storage but will it let me do so on browser is my question? I can’t see the option and it would be helpful right now in my situation to be able to purchase more storage or upgrade to iCloud+ on the browser if possible. Could someone let me know if it is please and thank you. -westcoastladyy