It is not letting me update

See https://support.apple.com/en-us/HT201435

BTW: while in this instance it wasn't a huge deal because there's a specific Apple resource about issues updating, in the future "it won't let me do XYZ" is not very informative for those of us trying to help. Additional information, like what exactly happens, would be beneficial on more obscure topics. Just food for thought.

Check these links...

If your iPhone, iPad or iPod touch won’t update - Apple Support

Updating iOS: common issues and solutions - Apple Community