How do I increase my storage?

you cannot increase your iPhone storage space if that's what you are asking..

If you want more iCloud storage space, you can upgrade your plan

Upgrade to iCloud+ - Apple Support

What's the difference between device storage and iCloud storage? - Apple Support

or see if this helps free up iPhone storage

You can’t purchase more storage for an iPhone; it will never have more than it did when you bought it. You will need to either buy a phone with more storage or take steps to optimize the storage on your phone→https://support.apple.com/kb/index?page=search&type=suggested&locale=en_US&q=optimize+storage&src=globalnav_support