First, take step 3. Do this as early as possible your 1st year. A good time to take it is around the inservice because you are already studying the stuff you need to know for the test. Sign up for it on the website: http://www.fsmb.org/usmle_applonline.html
Once you have your step 3 scores and you finish your 1st year, then you are ready to start your application for your license. I recommend using the Federal Credentialing Verification Service. This is a service run by the FSMB that will keep your licensing info in a safe database and send it out to whom ever you want for the rest of your life. Using it makes your Texas application easier because they gather a lot of your info for you and send it straight to the TMB. It does cost a little extra money though ($300). You can reach it at http://www.fsmb.org/fcvs_physapp.html
Once you get that set, then you can go ahead and start your application with the Texas Medical Board. The main application is online and costs around $850. You can reach the application at http://www.tmb.state.tx.us/
At some point you will need to send in a self-inquiry from the national practitioners databank (I think during the Texas licensing process). You can do that by going to http://www.npdb-hipdb.hrsa.gov/welcomesq.html
The TMB requires a jurisprudence exam for licensing. They will send you a slip that allows you to sign up for it. You do need to study a little bit. Ask around for a review book we have one in the department that gets passed down from year to year. You will also be required to get fingerprinted at some point during the process.
Once you get your license (8-10 months currently), then you still need your Texas DPS number, your DEA number, and your National Provider Identification number (Medicare/Medicaid number). Each costs more money, of course. You can reach these at:
Texas DPS: http://www.txdps.state.tx.us/criminal_law_enforcement/narcotics/pages/Controlled.htm
DEA: http://www.deadiversion.usdoj.gov/drugreg/index.html
NPI: https://nppes.cms.hhs.gov/NPPES/StaticForward.do?forward=static.npistart