Can anyone explain to me how I can reset my phone without a computer

Reset, or restore? Or is the iPhone disabled? You can erase all content and settings on the device, and then restore an iCloud backup, but if you need to restore the device because it is disabled, you need a computer for that. And if you have an iTunes backup instead of an iCloud backup, you would need a computer for that.

Any computer that has iTunes can be used to help initialize an iPhone. Any iTunes-equipped computer can facilitate restoring an iCloud backup file to your iPhone. However, only an iTunes-equipped computer that has your iPhone's backup file can restore that file to your "new" iPhone.