In the upper left of your HUD you should see a pair of numbers, a small one, and a larger one inside parenthesis. The small number should go up as the big number goes down. The small number is your number of recruits.
There should be a construction platform near your building which has your team colour. Once you have 15 recruits, construct a battle forge on that and produce units. Send those units to capture any nearby other construction sites. Capturing construction sites gives you bonus recruits. One of them should be an 8-sided platform called a Resource Construction Site. Build a Recruitment Citadel there once you have 20 recruits, and it will increase the rate at which you gain recruits.
