i advise that in future you do some reading before you get a animal, just because over the next few days your brain is gona have to process ALOT of information on axies (its hard to remember it all in such a short time, especially if you have a brain like mine lol), not to mention you now have to do even more work than normal to keep a axie ie water changes daily for ammonia spikes etc, but we are glad you found us and we are only too happy to help you learn what you need to give your axie a great home
www.axolotl.org is a great place to learn the basics and having a read over the other posts in the forum will give you some other tips you may find useful.
the minimum tank we advise for one axie is a 45x30x30cm tank, as said above the filter needs to be very soft, if your axies gills move when its away from the filter its too strong.
they like to eat things like earthworms, blackworms etc- having a read in the part about axie food will give you some good info on feeding. an adult doesnt need to be fed everyday, more like every 2-3 days, maybe every second for a juvie.
do not handle your axie unless you really need to ie moving tanks (better to use a net though), your skin can transfer nasty oils etc onto their skin and also damage their slime coat.
since you need to cycle your tank, as rob said, you will need to do at least 30% water changes daily to keep the ammonia in check if your axie is in it.
you can fill the tank up to the top if you wish, if it is make sure you have a lid though, my tank is 3/4 full, theres still 30cm of water though. axies dont mind plants really, they just absorb some of your nitrates, its a preference, i personally use plastic ones because i find my axies up-root them when they go on their little dashes.
as for substrate (what goes on the bottom) sand is best or no subsrate at all. some people like to use large river rocks but i find them annoying to clean. also some people cover the bottom in slate.
you will need to purchase the kits rob mentioned also, also a gravel siphon for water changes, and a thermometer. buckets will also be useful but make sure they have come in contact with no chemicals, also a turkey baster would be benifical to spot clean poops. oh and dont forget the water dechlorinator. a airpump and diffuser (airstone) can also be of use.
hope this helped a bit and we hope you enjoy learning aboout your new pet, your going to have hours of fun with it! also any chance of a wee pic or two? we really are nosey buggers here lol