While you are cyling you should not be making water changes on a timed schedule, but based on ammonia and nitrite readings. These should be checked daily. Ideally you should use a drops test kit because they are far more accurate. You need a drops test kit for ammonia, nitrite and nitrate.
Initially you will see ammonia in your tank. Anytime you see .5ppm you should make a water change, and ideally even as low as .25ppm you should make a water change. Eventually ammonia will hit 0 and nitrites will spike. Continue testing and making water changes as necessary until nitrites hit 0 and you see some nitrates. This is when you know your cycle is complete. It will take 3-8 weeks. Nitrates are ok in small ammounts but should be kept under 20ppm. Once the tank is fully cycled weekly water changes of 20-50% should keep them reasonable provided nothing happens to your cycle and you're not overstocked.
And lots of others we're not allowed to link to.