If you are looking to upgrade your Chase Sapphire Preferred to a Chase Sapphire Reserve, all you need to do is call the number on the back of your card. There are also a couple of things you should take into consideration before contacting Chase.
For instance, if you have only had your Sapphire Preferred for less than a year, you will not be able to upgrade your card. You will also need to have at least $10,000 in available credit on your card. Your account should also be in good standing.
Note that even if you meet the above criteria, this does not guarantee that you will be approved.
You can learn more about upgrading Chase Sapphire Preferred to Chase Sapphire Reserve here.