I want to flash this radio update correctly but I'm lost. I'm running xionia recovery and my phone is already rooted, what are the steps exactly?
Also my phone is using the newer screen.
Well you can flash the radio-only update that LeslieAnn posted on the OP - which won't affect your current ROM or anything else. You should use IHO/Bobzhome recovery, dunno about xionia. Do NOT use Touch or Multi-ROM recovery or you may brick.
Problem is there is some doubt whether that radio-update really takes, because it doesn't show as updated afterwards when checking the radio version. Wraith discovered this and has been leading the investigation. Could be just the version tag that never updates (but the radio itself does) or maybe the whole thing is just placebo.
If you want to be sure, you have to install the complete update that VMU posted. There is a link a few pages back in this thread. If you're on a custom ROM and/or recovery, you have to install it twice to be sure.
The steps have been posted many times the last few days. mrg666 posted a nice check list a few pages back. Doing this will wipe everything (ROM, recovery, root) and requires a factory reset first (wipes data). So nandroid first.
After this, you have to root again, using jcase's Gordita exploit posted by Jerry in a separate thread here.
Wow, that was more Swyping than I intended ;-)
Edit: or you can wait another day for brotherswing's writeup. Probably a good idea...