Though St. Anthony first joined the Augustinian Order, he eventually left it when he was 26 years old and joined the Franciscan Order around 1220 in the hopes of becoming a martyr for his faith. Through his work in Padua in Italy, he became a loved and admired Saint in the Catholic Church, sharing the faith through simplicity — which led to him becoming a Doctor of the Church. St. Anthony’s Feast Day is traditionally celebrated on June 13th, but you can pray a novena to him any time. He is often invoked for helping to recover lost items, among other intentions.
Here are a couple of links to novenas to St. Anthony of Padua: