The fish in cycle has some specific steps to follow in order to grow the biofilter and keep the water chemistry safe for the fish. The process shouldn't take more than a month. You add some floating plants to help steady the water chemistry. You feed the fish a little every day and twice a week, you remove and replace a third of the tank water. You do this for three weeks to grow the bacteria. At the end of three weeks, you start changing half the water weekly for as long as you keep the tank. If you add fish, you increase the amount of the weekly water change. That's it.
"Fear not, my young apprentice. Just change the tank water."