reinstall the OS

[undefinederror]

The other day I was given a Sony Xperia Z1. This phone is model number is C6906
Android version is 5.1.1
Kernel version is 3.4.0-perf-gd26777b-00851-ga8b7b55 BuildUser@BuildHost #1
Build number 14.6.A.1.236

The phone has started to act up. I would like to start over fresh, and wipe everything, as if it was just pulled out of the box.
How do I reinstall the operating system?

Thanks!

(also, if you guys have any other tips about this whole android thing, I'd appreciate the knowledge)
Thanks!

 

[mhinc]

The other day I was given a Sony Xperia Z1. This phone is model number is C6906
Android version is 5.1.1
Kernel version is 3.4.0-perf-gd26777b-00851-ga8b7b55 BuildUser@BuildHost #1
Build number 14.6.A.1.236

The phone has started to act up. I would like to start over fresh, and wipe everything, as if it was just pulled out of the box.
How do I reinstall the operating system?

Thanks!

(also, if you guys have any other tips about this whole android thing, I'd appreciate the knowledge)
Thanks!

Typically you would go into your settings > Security and look for something that says Factory Reset or reset phone to default

 

[undefinederror]

Alright, I'll do that for now. Thanks

 

[Rukbat]

Factory reset just deletes anything you've put in there (personal data, apps, videos, music, etc.). If you want to reflash the OS, look in the Z1 section of XDA Forums for help. (I know how to flash a few manufacturers, but not Sony.)