With a soft intro similar to "The Legacy", the lyrics set the scene: a large group of people leaving their country of origin to find freedom and – hopefully! – fortune. The narrator explains that this is a flight from trouble they may face in their native land, which could be an indication that these are the religious nuts that Europe didn't want, leaving for America in the 16th, 17th and 18th Centuries. After all, they are praying all the way to their "golden promised land" (not that it did them any good anyway).
It is not clear what the talisman they're sailing by really is, but the main character seems to be the one guiding the fleet towards the new world. Ironically, he dies as they approach the new shore to safety. The "sickness" mentioned is probably scurvy, which is invariably lethal if untreated.
All in all, "The Talisman" is another of those great Iron Maiden maritime epics in the line of "Rime Of The Ancient Mariner" and "Ghost Of The Navigator"..