Wipe top 4 boxes in twrp.
(Cache, dalvik cache, system, factory reset.)
Something along those lines.
Anyways. Wipe and install the clean ROM zip file you downloaded. Reboot phone once it says successful.
Radios and modems are normally flashed separate.
In the future. I'm sure there Is a how to on YouTube
Hit that thanks after you join the clean ROM club
Sent from my SCH-I535 using xda app-developers app