cycle computer

with most computers I have seen, you have to hold one button for at least 2 seconds. Some of them, 4 seconds.
Just hold one button for 4 secs and see if display flashes. if not, try the other button.
As soon as it starts flashing, push the other button to swap between Mph & Kmh.
When Mph is displayed, hit the first button (the button you sat on for 4 seconds) to save this setting.
90% certain this will work.
Tell us how you go

Thanks for the reply, however I did try that and all I can do is set the time. Maybe I need to learn how to interpret Km/h.

You may be happy with Kmh however your computer's default tyre rolling distance will be different to your actual tyre rolling distance.
So it's desirable to calibrate it properly...
maybe try Specialised website, they may have downloadable Adobe Acrobat manuals. I know Cateye does, I got a manual for a mate once.
They could have a "contact us" link too.
They should be happy to help, a happy customer will keep buying their stuff.