In St. Peter's the confessionals are in the right transept area past the Pietà side; look for the sign on each confessional naming the languages the priest hears. The basilica's penitentiaries are religious assigned to the basilica, and the English confessionals are busiest in the hour before closing. You go through the ordinary security line to reach them; there is no separate entrance for confession.
The Vatican's Jubilee confession page listed San Salvatore in Lauro (Italian and English, every day) and Santo Spirito in Sassia, the Divine Mercy church a few minutes from the square (Italian and English Monday to Saturday evenings and Sunday 9:00 to 11:00 a.m.; Polish Sunday evening). The page did not say whether those schedules continue after the Jubilee closed on January 6, 2026, so confirm with the church or at the door. The same page notes that St. John Lateran, St. Mary Major, St. Paul Outside the Walls and the Gesù hear confessions in various languages on their own schedules; St. Paul's lists 10:00 a.m. to noon and 4:00 to 6:30 p.m.
Groups over 40 should contact the church ahead with the number of penitents. For the wider city, see where-can-i-go-to-confession-in-english-in-rome.