You will need to be certain that you have vehicle insurance in your own name for it. Also,see to it that you have that proof of insurance and a valid driver license and current inspection before you attempt the transfer.
Your divorce attorney may help you with this. Your ex may be asked to sign a specific form giving you the authority to transfer the title to your name. You should also get a certified copy of your divorce decree which shows that the vehicle has been awarded to you. Go to the county tax office with all of this documentation in order to transfer title. Be prepared to pay a title transfer fee. For more information see the Texas DMV website.
Remember that if you were awarded the debt on the vehicle it will be your responsibility to pay off any lien. If it was paid by your ex, be prepared to bring the release of lien with you to the Department of Motor Vehicles along with the other paperwork.