I don't have that camera, but on all of the other Hikvision's that I have, hit the Configuration tab, then 'Image' on the left, then the OSD Settings tab. Not sure if it's the same on that camera but it might be.
I had an opposite version on some firmware on one of mine--it was impossible to get text overlay on 1280; only if I did a higher res would it show at all. Was definitely a bug in 5.1.2 firmware. One of many, many bugs in that firmware.