Hiya!
In earlier conversations, you mentioned being worried about the floating.
Juveniles tend to behave a bit strange, and even some adult individuals just like to float. As long as it doesn't look like he's incapable of getting down, you'll be fine.
However, you also mentioned not knowing about tank cycling (or water values), which is much more important.
Axolotls poop. This produces ammonia.
Ammonia is toxic at low levels.
Luckily, there are bacteria who eat ammonia. They remove the ammonia and turn it into nitrites.
Nitrites are also toxic, even at low levels.
Luckily, there are bacteria who eat nitrites. They remove the nitrites and turn it into nitrates.
Nitrates are only harmful at higher levels, so you can remove it with water changes every now and then.
A tank with all of these bacteria is cycled: the bacteria eat the harmful stuff and leave you with nitrates.
All of these bacteria only start to grow when you actually have high levels of their food in the tank. That means, in order to get ammonia-eating bacteria, you need ammonia - in order to get nitrite-eating bacteria, you need nitrite, etc.
As such, to get a tank cycled takes time: the time to produce ammonia, time for bacteria to grow and produce nitrites, time for other bacteria to grow and produce nitrates.
Cycling a tank can easily take two months, and until it's cycled you are at risk of sudden ammonia spikes, which can be harmful to your axolotls.
Basically, you'd want to cycle your tank before you get the axolotls.
Since that isn't possible for you anymore, it's important to keep close tabs on the levels of ammonia and nitrites in your water. You can buy some simple tests for this at every aquarium store.
Make sure to regularly test the water for ammonia and nitrites, and to do water changes if the levels get too high, until your tank is cycled and safe!