Installing is not working

Hi there. Try the following to troubleshoot this issue:

Update iOS on iPhone - Apple Support

1) Turn off Wifi, then power off your phone, boot it back up and make sure to connect to a reliable network. Try to update

2) Make sure you have enough free storage for the update (find out how to find storage here: How to check the storage on your iPhone, iPad, and iPod touch - Apple Support)

3) If nothing else works, back up your iPhone, reset it, and then restore the backup and iOS should update during the set up process

Let me know if these work for you or don't.

You might not have enough empty storage for the update to install. Try moving unwanted videos and large files to a computer to free up space for the update.