Normal Racing
In a normal racing mission in "Assassin's Creed II," your goal is to beat your opponent to the race's endpoint. You have free reign over how you get from the start to the finish, but in most cases the non-playable characters take the shortest path available. It may take several attempts to complete each of the game's racing challenges.
The Church Race
The race in the opening moments of "Assassin's Creed II" is more of a tutorial than anything else; it is designed to be challenging but not so hard that new players cannot complete it. You are awarded more room to mess up in this race, and more chances to recover from mistakes, than in later levels. Take your time finding clean paths and you can complete the mission without cheating.
The Cheat
If you keep failing the church race or simply don't feel like completing it, there's a simple method for beating Federico to the top of the church. The endpoint of the race is actually on top of the church behind you at the start. Simply turn around at the beginning of the race and climb the face of the church to defeat Federico with minimal effort.
Future Races
Only a few races in "Assassin's Creed II" present you with such a simple mechanism for winning. Practice your free-running skills and build a familiarity with the various interactive items in the environment to understand how to find fast and efficient paths from one point to another. Without solid skills and an understanding of the free-running mechanics, you will find it very difficult to complete later races.