Welcome to BD.org, and congrats on your new addition!
First things first, you will need to do a lot of research on the proper care of your new pet. Luckily you've come to the right place...
I would suggest first carefully reading through our
care sheet http://www.beardeddragon.org/articles/caresheet/
and then spend some time browsing the forums for all the info you could ever need. If you have any questions, feel free to ask! there are plenty of experienced BD owners on here that will be happy to help.
Now, I should mention that I couldn't help but notice a few issues with your post...
I am a little concerned by the fact that you said your new pet was 3 years old and only 12" tip to tip? Could you have maybe meant to say 3 MONTHS old? If there wasn't a typo, I would do some serious research into what kind of care Blaze has received over the last 3 years. 12" seems extremely small for an adult as most fully grown BD's will range anywhere from 17-24" depending on their genes.
You will want to make sure Blaze is getting the correct UVB lighting, and calcium supplements on a daily basis along with a healthy diet of greens and insects (this is all explained perfectly in our care guide posted above)
A 20g tank is much, much too small for an adult beardie, and should only be used for a short period of time as a temporary habitat. a 55g tank would do and would be fairly cheap however 120g or 4'x2'x2' tank would be your best choice.
As for the lighting... Your beardie requires a full spectrum light for basking and every day living, this can be obtained with a regular household bulb, or even a household outdoor floodlight. you will need to test different wattage's, and distances to get the right temperatures as they require a basking spot of 100-110 degrees.
Secondly and even more importantly, you beardie MUST be supplied UVB via a separate fixture... Most members of this Forum will recommend that you use a tube style light called the ReptiSun 10.0. this is your absolute best choice for UVB output in smaller enclosures. Please be very very careful on your
UVB light choice as some of them are plain hazardous to your beardies health. avoid compact and coil style UVB lamps like the plague as they do not emit enough UVB and they can lead to ocular irritation, and sometimes blindness.
You will also want to avoid red heat bulbs at night, Beardies require dark for sound sleeping, and the red light can actually disturb their sleep, and lead to health issues later. your best choice for heat at night would be a CHE (Ceramic heat Emitter) these give off heat only and no light.
Hope this helps a bit, I trust you will have more questions after reading the
care sheet