Overscan problems (can't fix on TV)

[bprochford]

ok that answers the other thread's question I posted.

comment out or remove the line optargs=disp.screen0_output_mode=720p60 from /boot/uEnv.txt if you want 1080p

---

let me know how that went

I'm trying everything I can to remove the line above from uEnv.txt but the text file is read only, and I have no idea, even after a couple hours of searching how to edit that file. I'm a linux virgin, so please be patient with me if this question has an obvious answer that I'm missing. 

How do I edit the uEnv.txt file?

Thanks,
Brad