Clowns aren’t sexually mature until they are 2+ years old. Once they’re old enough, put a clay flower pot or piece of tile for them to lay eggs in. You’ll need to culture rotifers and phytoplankton (or buy it). You’ll need a hatch tank and a grow out tank. It’s definitely not a simple process, but there is lots of info available.
Clownfishes - Kindle edition by Wilkerson, Joyce D., Thomas A. Frakes. Download it once and read it on your Kindle device, PC, phones or tablets. Use features like bookmarks, note taking and highlighting while reading Clownfishes.