How do I purchase more storage immediately.

There are two types of storage, as indicated in the article listed in Related Articles. The iPhone storage is set when you purchase it and cannot be increased. All you can do is delete content to increase storage ability. iCloud is not really storage, it is the ability to sync content across devices. If you are seeing a warning that the iPhone storage is full, you will need to delete content to recover any space. If you are seeing a warning that iCloud is full, you can purchase more space by going here, Upgrade your iCloud storage plan - Apple Support