PARIS—Lionel Messi said on Wednesday he wanted to power Paris St Germain to their first Champions League trophy, putting the tearful farewell he bade to Barcelona behind him after signing a two-year contract with the deep-pocketed French soccer powerhouse. Messi joined the star-studded PSG as a free agent after Barcelona, where he begun and always imagined he would play out his career, acknowledged last week they could no longer afford him. Thousands of PSG fans thronged the side’s Parc des Princes stadium, daring to believe their team would now deliver the Champions League having hoovered up domestic titles since free-spending owners Qatar Sports Investment European arrived in 2011 but always fallen short of European soccer’s top prize. Messi said he was hungry to add more Champions League titles to the four he won with Barcelona. “That’s why I am here (to win trophies). It’s an ambitious club,” Messi told a …