The Scottish outfit, who reached the last 16 last term, start their campaign next month with a second qualifying-round tie against Cliftonville.
"Our main aim is to qualify for Europe as we all enjoyed playing in the Champions League so much. We all enjoyed playing in Europe last season in some fantastic games and we want the same again next season," Ledley told Sky Sports News.
"Hopefully the gaffer can keep hold of our best players and bring players in to make us better. We know it is going to be difficult with the teams who we can play in the qualifying rounds. We need to be up for it and that is why we have come back early so we can be fit and ready for it."