using flash

I am an amateur phptogrpaher. Should I use a flash in the morning hours or it should be used only at night?

that's a pretty vague question - it all depends on the light you have to work with.

You can use your flash anytime during the day for "fill flash" if you are wanting to fill in the shadows with some light. But if you are wanting to do silhouettes, then I would not use a flash.

Your camera guide should give you directions on how to use fill flash during the day. It could also be under back-lighting as well. But it does depend on your camera model. A lot of cameras, if you are shooting into the direction of the morning sun for example, will think there is enough light. So depending on your camera model, will depend on whether you use fill flash or back-lighting compensation/auto flash modes.