The instructions on here say (in quick summary) -
Add enough ammonia to get 3 ppm
Test until you get ammonia less than 0.75 AND nitrite above 2 ppm
Add enough ammonia to get 3 ppm
Test every other day and when you have 0 ppm ammonia then 0 again 2 days later add enough ammonia to get a reading of 1 ppm
Test until you have ammonia less than 0.25 AND nitrite less than 1.0.
Then add enough ammonia to get 3 ppm
If you have 2 zeros next day the cycle is finished. But if you don't have two zeros, wait until ammonia is under 0.25 AND nitrite is under 1.0 and add another 3 ppm ammonia.
Test 24 hours later. If both are zero, the cycle is finished. If you don't have 2 zeros, wait until ammonia is under 0.25 and nitrite under 1.0 and then add 3 ppm ammonia.
And so on until you have two zeros.
Which stage are you at?
@steelo I would do a water change. You mustn't let nitrite get high enough to stall the cycle.