Default How to select my network?

I just got this phone last night. The lady told me that it was supposed to be unlocked and they had put in straight talk sims with success. I have cincinnati bell and i tried putting my sim card in it and nothing registered. i put it in gsm mode and nothing happened. i usually have to physically go in and select my network but i couldn't find that option at all. where is the option to select your mobile network?