Iphone 6

You don't, sorry. If you don't have a computer, borrow one from friends/neighbors/relatives or ask for help at an Apple Store or Autorized Service Provider. Then read this:

Given that to remove the existing passcode you must connect your device via USB to a computer (a Windows PC running the latest iTunes version, or a Mac, which can run iTunes or Finder, depending on the macOS installed on it), and keeping in mind that if you don't have a backup all data will be lost on that device (except those that you eventually synced to iCloud), pay attention to the specific gestures that you need to perform while connecting your device to the computer.

These are the instructions to re-gain access to your iPhone/iPad:

If it is an iPhone:--> If you forgot your iPhone passcode - Apple Support

If it is an iPad:--> If you forgot the passcode on your iPad, or your iPad is disabled - Apple Support

Or, watch this support video about the same matter (for both iPhone and iPad):

https://www.youtube.com/watch?v=7s8-zLG9ySQ

Regards

Giulio

You borrow a computer, or you contact and work with Apple or an Apple authorized repair provider.