I can provide you some basic information about Dental Assistant in Texas.
First of all, you need to have CPR certification from one of the DANB accepted providers.
Secondly, you need to take one of the RDA approved course and pass it.
Finally, you need to have SSN to register as a Dental Assistant in the State of Texas.
All information is here:
http://www.tsbde.texas.gov/node/135.html
Once you are registered you can volunteer or look for opportunities in various dental offices where they can provide you on-the-job training. If you get accepted, well and good. If not, I would suggest you to take DANB's CDA certification exam to prove your ability. At the same time, look for volunteer opportunities as a dental assistant.
What is your ultimate goal? Do you want to be a dentist or settle as a Dental Assistant?
Ask me specific questions and I will be able to answer them for you.