It will be Marshall's first season in the top-flight.
"Itâ€™s going to take a bit of getting used to," he told the Western Mail.
â€œIâ€™m expecting a whole new challenge and Iâ€™m preparing for that now.
â€œAt Championship level there were always a lot of crosses coming into the box, but I donâ€™t expect the same number in the Premier League.
â€œThe best teams will look to play their way through rather than fire it into the penalty area early.
â€œIâ€™ll find that out for myself over the next few months but I have spoken to goalkeepers who have played in the Premier League."