If you've already put plants in your tank, make sure you don't dose with too much ammonia.
To start your cycle, fill your tank with dechlorinated water, and then provide it with an ammonia source (this can be pure ammonia or fish food that will slowly decay and cause an ammonia spike). If you've already put plants in your tank, make sure you don't dose with too much ammonia. Even though it's used as a plant fertilizer, it can cause damage/melt in high amounts. Ammonia also has a greater effect in warm, acidic tanks, so keep that in mind. Test your water regularly and monitor how ammonia, nitrite, and nitrate levels change over time.