Free download and install FoneEraser for iOS on your computer and then it will get launched automatically once the installation is finished. Then you need to onnect iPhone to computer.
2Quick Scan Mode
Click Quick Scan after connection. Then it shows all items can be freed up. You can click Erase button on the right side to speed up iPhone.
You can also choose Erase Junk FIles, Uninstall Applications, Delete Large Files or Clean Up Photos on the left side. After selection, detailed itmes appear on the interface. You can remove selective data with ease.
1Choose Erase All Data
Choose Erase All Data on the main interface.
2Turn Off Find My iPhone
If you have enabled Find My iPhone feature, please follow the on-screen instructions to turn it off.
3Select Security Level
Choose Low, Middle or High from the options and click Start. Please notet that all data will be erased and they are unrecoverable.
Type 0000 in the box and click Erase button.