To talk about a time in the morning, you can use the abbreviation "a.m.":

10:30 a.m.

It's correct to put periods after the 'a' and 'm', but recently more and more people write it like this:

10:30am

The abbreviation for a time after noon is "p.m."

When you're speaking out loud instead of writing, using "a.m." and "p.m." makes the time sound quite exact. A less formal way to speak is to drop the abbreviation when it's obvious:

I wake up at about nine.

Or use "in the morning", "in the afternoon", etc.

I slept until three in the afternoon.