The long version requires a degree in biochemistry, so I'll give you the short version:
Axies (and fish) produce waste called AMMONIA which is harmful. In order to process this waste you need to grow good bacteria in your filter to break AMMONIA down. AMMONIA breaks down into NITRITE, but this is also harmful, so you need to grow another bacteria to process it into NITRATE. NITRATE is only toxic in higher concentrations, you remove this by changing some of the water every week.
How to do it?
Get a master test kit - liquid not test strips.
Set up your tank - substrate, ornaments, filter. Add dechlorinated water. No animals, no plants.
Add pure ammonia one teaspoon at a time until your test for ammonia reads 4ppm
test daily until all the ammonia is gone, them add more ammonia to get it back up to 4ppm
after the 2nd dose of ammonia you need to test for nitrites as well as ammonia
you should be seeing ammonia reducing regularly and nitrites increasing at this point
continue dosing once ammonia is gone, this should be every 2 or 3 days by now
After about 3 weeks you need to start testing for nitrates. Once you start seeing nitrates you're nearly there.
One day you will dose with ammonia, then the next day your test will read ammonia 0 nitrite 0 and nitrates sky high.
Your tank is now cycled, you need to do a really big water change (90%) and then you're ready to add your animals.
