LG TV apps are published through LG Seller Lounge. There's nothing to sign: you upload the package from your control panel and LG signs it when you submit. The part that takes patience is LG's quality check, which runs for several weeks.
LG updates Seller Lounge from time to time. If a label below doesn't match your screen, look for the closest one that means the same thing.
Updates later: build LG again in your control panel, upload the new .ipk, refresh the checklist if LG asks, and submit. LG checks every update again, so leave time before a launch date. New videos and changed links don't need an update at all.