How will I buy space for my phone
ho can I buy space for my phone
iPhone 6, iOS 12
You don't, the storage on an iPhone is a fixed size and can't be increased.
Here are some helpful articles that can guide you on how to free up storage space on your phone.
How to check the storage on your iPhone, iPad, and iPod touch - Apple Support
How to check the storage on your iPhone, iPad, and iPod touch - Apple Support
Manage your photo and video storage - Apple Support
Manage your photo and video storage - Apple Support
Clear Other storage on your iPhone or iPad - Apple Support
Clear Other storage on your iPhone or iPad - Apple Support