How do I update my iPhone 6s to iOS 15?

mysis192 wrote:

I want IOS 15 update

Please see: Update your iPhone, iPad, or iPod touch - Apple Support

And: If your iPhone, iPad, or iPod touch won't update - Apple Support If the above Apple articles do not help, please post back with relevant information. 

then you should update your iphone

this is how

Update your iPhone or iPad - Apple Support

I want to update my IOS 15

Danieloluwadara8 wrote:

I want to update my IOS 15

Assuming you have a compatible device, the steps to do so have been provided above.