Bulova Marine Star 96C30 watch "blinking thing upper left hand" Questions

upper left) The "C" button is at the 8 o'clock position (lower left) The "M" (mode) button is at the 4 o'clock position (lower right), and is the only button you can pull out to set the times,

...thing at a thrift store, and I can't set the time. The default time shows military standard time, and I can't change it. Please help, thank you. I just dug my watch out after not wearing for a few ...