The problem with most fish tanks is they are too narrow. You need at least 18" deep and 24" is better. The length and height are probably OK. Is Harry a baby or a full-grown beardie? You can expect him to be somewhere over 20" when grown, so a 13" fish tank isn't a very good fit.
The glass lid will have to go, as glass blocks
UVB light, and a fully closed tank will likely be too airtight and way too hot. You'll need a screen top. You'll need a ReptiSUN 10.0 fluorescent tube
UVB light and a fixture. Don't let the pet shop talk you into anything else. You will need some sort of a heat lamp to bring the basking area temperature up to around 105 degrees F. That should be on one side of the tank. The other end should be allowed to drop to around 85 degrees and is called the "cool side". For basking, you will want some sort of branch or ledge. Just be sure it is stable - a pile of rocks may not work well.
You'll need a substrate - non-adhesive shelf paper or floor tiles are good. No sand or other particulates. You'll need a good digital thermometer with humidity readout. You can get them at Lowes for around $12 with a wired probe. Run the wire to the basking spot, hang the unit in the cold spot and you have it all covered.
You may want a water dish - some use them and some don't. You may want a hide of some kind. Again, some dragons use them and some don't.
You'll obviously want food - crickets, repti-worms or phoenix worms. Meal worms are not good. Anything you feed should be sized about the distance between his eyes. You'll need a salad bowl, and the salad. Collard greens are good, squash, carrots in moderation. Plain lettuce is not good for them. You will also need ReptiCAL calcium powder and Herptivite vitamin powder. Dust the live feeders with calcium 5 times a week, with the vitamins 2x a week.
You'll need to give him a
bath about every other day or so, so plan on a container for that. Then there's cleaning supplies: paper towels, disinfectant, etc. for cleaning the poop and the cage. Keep some hand sanitizer around for you, as they can carry salmonella in some cases.
As the weather warms up, you might want a leash and harness for him to take him out with you. And don't forget the initial vet checkup to make sure he's healthy and parasite-free.
Good luck and post pics!