hi harris, try this
1. connect phone to pc
2. see usb icon on shortcut drop down, you see message : charge only , usb storage , go to pc-software and press ok.
3. go to settings menu- press applications - press development now you can press usb debugging press ok
USB debugging options should be able to tick.
If u want to root, you can use this link
Root LG Spectrum Smartphone Method By Dan Rosenberg
beforehand, you need to install L3 USB driver, find it from LG E400 Support: Find Manuals & Warranty Info | LG UK
click the software update & drivers
nubie First-timer superuser