Follow the tutorial in the game would help you to play Fort Defense Saga easily. It is simple and clear.
There are many sites in each level, press it and select the tower you want to build. If the number is in red, you need to collect more money to build it.
In some maps, there will be some locked sites, use the barrels to access it. The barrels can be earned when you finished one battle. Please remember that, take care of your barrels, since it is useful to upgrade your tower’s attributes!
When the enemies are getting stronger, you should upgrade your towers either!
The health (Heart) will be reduced if there are enemies breaking out your defense. If you want to collect more barrels and stars, please keep raising your guard! The enemies are Fickle and Tricky!