once you have the tank full, you can fire up the filters. its an all in one tank so just make sure there is floss wherever the water goes in to start clearing it up. it might take a couple hours (or more) but the water will clear up.
you can install the heater anytime (nothing alive to get hurt from temperature changes) after the tank is full. once everything clears up, i would add some carbon and either microbacter7, fritz fast start or whatever tiny bottle of fishpoop they can charge you $20 for. or/and you can throw half a shrimp or a large pinch of fish food to get the cycle rolling.
After that, you have really hurry up and... wait. and wait some more. you can test for ammonia, after the ammonia goes back down to normal the nitrite will jump, once that goes down, you get to the nitrate part of the cycle and once that's done, you can add living things.
you will hear some different timelines like "it will only take a week" and so on and it might but the test tell the story as to when the tank is ready. Normally it takes up to 4 weeks. anyways, after all that has happened and you add fish or whatever, there usually comes an algea bloom or two. don't get discouraged. they also don't last and will eventually go away.