Complex sentence: Barcelona first participated in the 1979 edition after they won the 1978 Cup Winners' Cup, however they lost 1--2 to Nottingham Forest on aggregate, drawing 1--1 in Camp Nou after losing 0--1 in City Ground, Nottingham.
Split into simpler sentences: Barcelona first participated in the 1979 edition, after they won the 1978 Cup Winners' Cup. They lost 1--2 on aggregate to Nottingham Forest, having drawn 1--1 in Camp Nou after losing 0--1 in City Ground, Nottingham.