I trying to work out how to use my ti83 plus -What is the pH and pOH of a 1.2 x 10 -3 HBR solution?

First you have pH+pOH=14
Thus pOH=14-pH.
The problem with you question is that you do not specify the meaning of the 1.2 x 10^(-3). Is it the molar concentration of the hydrpbromic acid HBr.

I am going to answer your question but I must make some assumptions. You can imitate the reasonning to obtain your answer, once you have decided or looked up what the numbers mean.

Lets assume that HBr concentration is 1.2x10^(-3) mol/L. Since it is a strong acid, it dissociates completely, releasing 1.2x10^(-3) mol/L H+/H3O+ ion.
Thus the pH is
pH=-log(1.2x10^(-3)).
The result is 2.92

Here is a screen capture of the actual calculation. The minus signs are the change sign (-) to the right of the dot. To enter the power of 10 (represented by the E in display) use the (2nd)(EE) key sequence. To access the content of (Ans) memory, press (2nd) (change sign)