HELP! can't install custom rom

[AC Question]

ok, I'm a bit of a noob so take it slowly.
I forgot to put ROM on sdcard, on twrp, wiped system so I can't boot into system. Internal memory not showing up on PC to put in installation files. ADB sideload say's device not found. OTG USB drive not showing up in TWRP. now stuck in recovery with no system ROM

Using Xperia S
TWRP 2.7.1.0
when powering on, goes into recovery.
Able to get fastboot mode but can't find any files to flash.
Can't find CWM for xperia S.
Device not showing up in Sony's Emma program to get back to stock when in recovery or fastboot

Help and thanks