First look online or in a local phone book for someone that is near the courthouse in Fort Bend County. If you have never been in trouble the you will qualify for what is called a deferred probation. Once you complete that, then you can have the case file "non-disclosed". That keeps it off public records.
There are a few other possibilities that an attorney could go over with you.
More than likely the paper you signed was a Criminal Trespass warding. That means you have to stay away from the store or take a chance getting arrested for Criminal Trespass.
Look for a local criminal defense attorney in your area, either on avvo or online. If your record is clear you can likely negotiate a deferred or some pretrial diversion program. If you can sucessfully complete the program the charges will be dismissed with no finding of guilt. As noted you can then move to have the charge sealed. A theft conviction is serious and you need to take steps to avoid having this on your record.
Good luck, and if you need the names of local attorneys feel free to email me.
You should consider applying to the prosecutors' office for pre-trial diversion. It depends on your history, the facts of the case, etc. on whether on not they will consider it. If so, then it would keep your record clean. (Not exactly - you would enter a contract for a certain term to do certain things. Once that term is over, if you have successfully completed everything, then the case is dismissed. You must then wait the prescribed period to expunge it - if the county in which your case is pending allows it. Harris County does.)
The other lawyers told you how to look for a lawyer. Talk to the candidates about pretrial diversion. Deferred would be then next step, though no nearly as good.
First there are a few options on keeping this off your record. You should discuss them with who ever you hire. Deferred adjudication probation and pre-trial diversion are both options that will keep your record clean.
As far as hiring a lawyer the internet is a great starting point. Find lawyers who practice in Fort Bend County and then call them and interview them and find one you like.