Well I havent used the archers recently, but i use the wizards. First you need to buy a temple, after buying a temple you can drop guys into the castle and convert them onto your side. Once you see little blue stick figures by the Castle's health bar, you can click on a flag on top of the castle, and make the converts either archers, wizards, etc.
wow, I got to level 13, I believe... when that giant guy came abd got me in short order.
I had 11 archers, that helped... until I started racking up casualties, then I couldnt get enough people to be suicide bombers and archers, let alone anything else...