airport to St Mark's Square Linea Arancio (Line A) every 30min and takes 1hr to get to S'Angelo and costs around 15€ see map of routes
Venice Airport Bus Express to Venice Piazzale Roma which is next to Venice Santa Lucia station (on the island of Venice) takes 35min and buses are generally every 20 minutes and costs around 8€: ATVO VENEZIA EXPRESS ACTV urban bus line 5.